feat: allow dates before 1970

[SebastianKrupinski]

• Resolves:

• Can't select dates older than 1 Jan 1970 or newer than 2038 calendar#6818
• [Bug]: Calendar Frontend is not able to handle Events before 01.01.1970 calendar#6912

Summary

• added migration to change unsigned fields to signed
• removed date restriction in backend

This fix essentially only effects MariaDB and MySql as PostgreSQL, SQLite and Oracle store int values as signed and are not affected.

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)
• Labels added where applicable (ex: bug/enhancement, 3. to review, feature component)
• Milestone added for target branch/version (ex: 32.x for stable32)

[ChristophWurst]

unsigned to signed means the value range halves and on mysql/mariadb outliers are silently clipped. but that is fine because we already use bigint so the range is big.

the risk of this change is that mysql/mariadb have to rebuild the table. the old and new data type have the same size, but their layout isn't identical.

nextcloud/calendar#6818 also mentions a 2038 limit. bigint does allow later dates. is this restricted elsewhere?

[SebastianKrupinski]

nextcloud/calendar#6818 also mentions a 2038 limit. bigint does allow later dates. is this restricted elsewhere?

Yes, there are date limits in the calendar and other places that will need to be removed. The 2038 limit is a 32bit int limit, that can be removed also.

[ChristophWurst]

How do we handle dates past 2038 on 32 bit systems?

[SebastianKrupinski]

How do we handle dates past 2038 on 32 bit systems?

We don't lol, 32bit is dead. Intel / AMD 64bit came out in 2000, ARM was 2011.

Most Linux distros are dropping or have dropped 32bit versions, MS has stopped 32bit in 2020.

[ChristophWurst]

Nextcloud does support 32bit systems. Older Raspberry Pi for example. This is also why the 64bit integer for snowflakes will be stored in a string instead of int.

[ChristophWurst]

Nvm, looks like timestamps are explicitly exempt from the 32bit support: https://docs.nextcloud.com/server/stable/admin_manual/installation/system_requirements.html#cpu-architecture-and-os

32-bit systems are supported, with the following known limitations:

Dates before Unix Epoch (1970-01-01) are not supported

Dates after 2038 are not supported