Revert "Various calendar-related cleanups (breaks "add/edit event" for now)"

This reverts commit 227c401d1934d6da34d9eca5aff971e78f0a7641.
Revert "Minor CSS tweaks for the Calendar"

This reverts commit 1e91de794e84016b87d77722a82cc4f2a3671186.
Revert "Make the yearly archive pages a bit nicer"

This reverts commit 2f09cac4ffe072efe49fb805cc7566c6fd38427f.
Revert "Event archive: Align years a bit nicer"

This reverts commit 46c0d8a8ba6118821c7e52b34c4b35a23087e91a.
Revert "Clean up and simplify the monthly calendar"

This reverts commit a0bdba4c9c015f05a215667372fa0ff3058cd67a.