I have been playing this game since yesterday at 10 am. (specific time) I haven't seen him since yesterday. (more general time)
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.
I have been playing this game since yesterday at 10 am. (specific time)
I haven't seen him since yesterday. (more general time)
They don't have to be specific. "Yesterday" and "last week" are suitable points in past time, as would be "last year" in "I haven't seen Kim since last year".
One common error with "since" is using it to denote a period of time. e.g. *"I have been living here since five years", or *I am in London since three weeks".