1. Saturday is a fun day for many students.

2. Saturday is a fun day to many students.
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Which one is correct? Can we use both sentences?
What is the difference because of 'for' and 'to'?

1 answer

If you put the "to" phrase at the beginning of the sentence, the two sentences would almost mean the same thing.

To many students, Saturday is a fun day. (meaning those students think it is)
Saturday is a fun day for many students. (meaning many students have fun on Saturdays)

Always look up words in a good dictionary when you're unsure of their meanings:
https://www.dictionary.com/browse/for
and
https://www.dictionary.com/browse/to?s=t