Turns out that recently we accidentally introduced a new behaviour of date-pickers on:
the bookmark modal
the topic timers modal
In fact, all other date-pickers always choose the first day of the next month when picking the Next Month option. This is the default behaviour. The ability to choose a day exactly in one month from today is important too, but it isn’t among our defaults, so the calendar should be used for doing this.
So we won’t change the behaviour of the suspension modal, moreover, we returned the pickers on the bookmark modal and the topic timer modal to our defaults in this PR: