English teachers love to explain the difference between the use of ‘for’ and ‘since’ when indicating the amount of time after an event; students love it, too. It is an easy grammar rule to communicate to students and is easy enough to understand.
‘For’ with a period of time. ‘Since’ with a date and time.
That’s the usual explanation and understanding and it is straight forward enough, so why do so many learners forget the rule while speaking and writing in English?
I suggest it’s because the rule is arbitrary. It could easily be the other way around. Why not since for a period of time and for with a date and time?
The best way to teach and to remember arbitrary rules of language is with simple mnemonics. These memory aids act in place of a logical rule when there is no reason for a specific grammar rule to exist.
With the rule regarding the use of ‘for’ and ‘since’, the best mnemonic is the letter ‘e’.
This video explains how it works…