217 lines
10 KiB
Markdown
217 lines
10 KiB
Markdown
---
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eip: 1872
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title: Ethereum Network Upgrade Windows
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author: Danno Ferrin (@shemnon)
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discussions-to: https://ethereum-magicians.org/t/eip-1872-ethereum-network-upgrade-windows/2993
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status: Stagnant
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type: Meta
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created: 2018-03-25
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---
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## Simple Summary
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A proposal to define a limited number of annual time windows in which network
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upgrades (aka hard forks) should be performed within. Policies for scheduling
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network upgrades outside these windows are also described.
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## Abstract
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Four different weeks, spaced roughly evenly throughout the year, are targeted
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for network upgrades to be launched. Regular network upgrades should announce
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their intention to launch in a particular window early in their process and
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choose a block number four to six weeks prior to that window. If a network
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upgrade is cancelled then it would be rescheduled for the next window. Not all
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windows will be used. Priority upgrades outside the roadmap may be scheduled in
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the third week of any month, but such use is discouraged. Critical upgrades are
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scheduled as needed.
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## Motivation
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The aim of this EIP is to provide some level of regularity and predictability to
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the Ethereum network upgrade/hard fork process. This will allow service
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providers such as exchanges and node operators a predictable framework to
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schedule activities around. This also provides a framework to regularize the
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delivery of network upgrades.
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## Specification
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Scheduling is defined for three categories of network upgrades. First are
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`Roadmap` network upgrades that include deliberate protocol improvements. Next
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are `Priority` network updates, where there are technical reasons that
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necessitate a prompt protocol change but these reasons do not present a systemic
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risk to the protocol or the ecosystem. Finally, `Critical` network upgrades are
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to address issues that present a systemic risk to the protocol or the ecosystem.
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### Roadmap Network Upgrades
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Roadmap network upgrades are network upgrades that are deliberate and measured
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to improve the protocol and ecosystem. Historical examples are Homestead,
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Byzantium, and Constantinople.
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Roadmap network upgrades should be scheduled in one of four windows: the week
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with the third Wednesday in January, April, July, and October. When initiating a
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network upgrade or early in the planning process a particular window should be
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targeted.
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> **Note to reviewers:** The months and week chosen are to provide an initial
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> recommendation and are easily modifiable prior to final call. They thread the
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> needle between many third quarter and fourth quarter holidays.
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Implementors are expected to have software for a Roadmap network upgrade ready
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two to four weeks prior to the upgrade. Hence a block number for the network
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upgrade should be chosen four to six weeks prior to the network upgrade window.
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Scheduling details such as whether this choice is made prior to or after testnet
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deployment are out of scope of this EIP.
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Depending on the release cadence of Roadmap network upgrades some windows will
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not be used. For example if a six month release cadence is chosen a roadmap
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upgrade would not occur in adjacent upgrade windows. Hence for a six month
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cadence if a roadmap upgrade occurred in April then the July window would not be
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used for network upgrades.
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If a planned roadmap upgrade needs to be rescheduled then strong consideration
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should be given to rescheduling the upgrade for the next window in three months
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time. For the case of a six month cadence this may cause releases to be in
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adjacent release windows. For a three month cadence the next network upgrade
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would be merged with the current upgrade or the next network upgrade would be
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delayed.
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To be compatible with the scheduled release windows the cadence of the Roadmap
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Network Upgrades should be a multiple of three months. Whether it is three, six,
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nine, or more month cadence is out of scope of this EIP.
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### Priority Network Upgrades
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Priority network upgrades are reserved for upgrades that require more urgency
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than a roadmap network upgrade yet do not present a systemic risk to the network
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or the ecosystem. To date there have been no examples of a priority upgrade.
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Possible examples may include roadmap upgrades that need to occur in multiple
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upgrades or for security risks that have a existing mitigation in place that
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would be better served by a network upgrade. Another possible reason may be to
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defuse the difficulty bomb due to postponed roadmap upgrades.
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Priority network upgrades are best launched in unused roadmap launch windows,
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namely the third week of January, April, July, and October. If necessary they
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may be launched in the third week of any month, but strong consideration and
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preference should be given to unused roadmap launch windows.
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Priority network upgrades should be announced and a block chosen far enough in
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advance so major clients implementors can release software with the needed block
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number in a timely fashion. These releases should occur at least a week before
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the launch window. Hence priority launch windows should be chosen two to four
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weeks in advance.
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### Critical Network Upgrades
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Critical network upgrades are network upgrades that are designed to address
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systemic risks to the protocol or to the ecosystem. Historical examples include
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Dao Fork, Tangerine Whistle, and Spurious Dragon.
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This EIP provides neither guidance nor restrictions to the development and
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deployment of these emergency hard forks. These upgrades are typically launched
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promptly after a solution to the systemic risk is agreed upon between the client
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implementors.
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It is recommended that such upgrades perform the minimum amount of changes
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needed to address the issues that caused the need for the Critical network
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upgrade and that other changes be integrated into subsequent Priority and
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Roadmap network upgrades.
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### Network Upgrade Block Number Choice
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When choosing an activation block the number can be used to communicate the role
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of a particular network in the Ethereum Ecosystem. Networks that serve as a
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value store or are otherwise production grade have different stability concerns
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than networks that serve as technology demonstration or are explicitly
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designated for testing.
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To date all Mainnet activation blocks have ended in three or more zeros,
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including Critical Network Upgrades. Ropsten and Kovan initially started with
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three zeros but switched to palindromic numbers. Rinkeby has always had
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palindromic activation blocks. Goerli has yet to perform a network upgrade.
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To continue this pattern network upgrade activation block numbers for mainnet
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deployments and production grade networks should chose a number whose base 10
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representation ends with three or more zeros.
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For testnet and testing or development grades network operators are encouraged
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to choose a block activation number that is a palindrome in base 10.
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Block numbers for Roadmap and Priority network upgrades should be chosen so that
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it is forecast to occur relatively close to Wednesday at 12:00 UTC+0 during the
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launch window. This should result in an actual block production occurring
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sometime between Monday and Friday of the chosen week.
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## Rationale
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The rationale for defining launch windows is to give business running Ethereum
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infrastructure a predictable schedule for when upgrades may or may not occur.
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Knowing when a upgrade is not going to occur gives the businesses a clear time
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frame within which to perform internal upgrades free from external changes. It
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also provides a timetable for developers and IT professionals to schedule time
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off against.
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## Backwards Compatibility
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Except for the specific launch windows the previous network upgrades would have
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complied with these policies. Homestead, Byzantium, and Constantinople would
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have been Roadmap Network Upgrades. There were no Priority Network Upgrades,
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although Spurious Dragon would have been a good candidate. Dao Fork was a
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Critical Network Upgrade in response to TheDao. Tangerine Whistle and Spurious
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Dragon were critical upgrades in response to the Shanghai Spam Attacks.
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Constantinople Fix (as it is termed in the reference tests) was in response to
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the EIP-1283 security issues.
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If this policy were in place prior to Constantinople then the initial 2018
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launch would likely have been bumped to the next window after the Ropsten
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testnet consensus failures. The EIP-1283 issues likely would have resulted in an
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out of window upgrade because of the impact of the difficulty bomb.
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<!-- ## Test Cases -->
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<!-- no test cases are relevant for this EIP -->
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## Implementation
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The windows in this EIP are expected to start after the Istanbul Network
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upgrade, which is the next planned Roadmap upgrade. Istanbul is currently slated
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for mainnet launch on 2019-10-16, which is compatible with the schedule in this
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EIP.
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The Roadmap Upgrade windows starting with Istanbul would be as follows:
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| Block Target | Launch Week Range |
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| ------------ | ------------------------ |
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| 2019-10-16 | 2019-10-14 to 2019-10-18 |
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| 2020-01-15 | 2020-01-13 to 2020-01-17 |
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| 2020-04-15 | 2020-04-13 to 2020-04-17 |
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| 2020-07-15 | 2020-07-13 to 2020-07-17 |
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| 2020-10-21 | 2020-10-19 to 2020-10-23 |
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| 2021-01-20 | 2021-01-18 to 2021-01-22 |
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| 2021-04-21 | 2021-04-19 to 2021-04-23 |
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| 2021-07-21 | 2021-07-19 to 2021-07-23 |
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| 2021-10-20 | 2021-10-18 to 2021-10-22 |
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| 2022-01-19 | 2022-01-17 to 2022-01-21 |
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| 2022-04-20 | 2022-04-18 to 2022-04-22 |
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| 2022-07-20 | 2022-07-18 to 2022-07-22 |
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| 2022-10-19 | 2022-10-17 to 2022-10-21 |
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The Priority windows through next year, excluding Roadmap windows, are as
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follows:
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| Block Target | Launch Week Range |
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| ------------ | ------------------------ |
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| 2019-11-20 | 2019-11-18 to 2019-11-22 |
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| 2019-12-18 | 2019-12-16 to 2019-12-20 |
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| 2020-02-19 | 2020-02-17 to 2020-02-21 |
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| 2020-03-18 | 2020-03-16 to 2020-03-20 |
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| 2020-05-20 | 2020-05-18 to 2020-05-22 |
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| 2020-06-17 | 2020-06-15 to 2020-06-19 |
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| 2020-08-19 | 2020-08-18 to 2020-08-21 |
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| 2020-09-16 | 2020-09-14 to 2020-09-18 |
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| 2020-11-18 | 2020-11-16 to 2020-11-20 |
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| 2020-12-16 | 2020-12-14 to 2020-12-18 |
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## Copyright
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Copyright and related rights waived via [CC0](../LICENSE.md).
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