Some timestamp tests won't work on the last day of a month and probably also not on the first day:

https://integration.wikimedia.org/ci/job/pywikibot-core-tox-nose/2267/console

• TestTimestamp.test_add_timedelta will fail on the last day
• TestTimestamp.test_sub_timedelta should fail on the first day

But I'm not sure what the best way to fix this is, without simply disabling them. One way to disable them only on the last/first day is, to compare the months of t2 and t1 and skip them if they are different.