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'?
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