From time to time means occasionally, without any pattern. Sometimes, and you could not say when.
The absence of a pattern is what distinguishes it from regularly, since something that happens from time to time is unpredictable. It sits at the start or the end of a clause. It is slightly more formal than now and again and considerably more so than every so often. Contracts use it a great deal, since a rule that may be amended from time to time is one that can change at any point.
1phrasefrom time to timeOccasionally and at irregular intervals.
“He still writes from time to time.”
Also accepted in games: every now and then
Practised in Time & Calendar, A Man Called Ove
First appears in chapter 28 of A Man Called Ove.
Practise this word