since, henceforth
Time-related Noun +
Noun +
When attached directly to a noun representing a point in time or an event, it marks the starting point of a continuous state.
先月
I have been busy since last month.
月曜日
It has not rained since Monday.
Verb て form +
When used with a verb,
The て form of the verb combined with
この学校に入学して
I haven't seen him since I entered this school.
日本に来て
He has been living alone since he came to Japan.
The clause following