This is a common grammar mistake that even native English speakers will make when writing. When do we use "its" and when do we use "it's"?
ITS shows possession for the pronoun 'it'
IT'S is the contraction for 'it is' or 'it has'
"The college has its graduation ceremony at 10:00am." In this sentence, possession is shown. So there is no apostrophe in 'its.'
"It's raining cats and dogs outside." In this sentence, 'it's' could be replaced with 'it is,' so we need to use an apostrophe.
If you are ever in doubt, replace 'it's' with 'it is' or 'it has.' Does it make sense? If so, use the apostrophe. In our first sentence, this wouldn't make sense: "The college has it is/has graduation at 10:00am." So we know we are showing possession, and we must not use the apostrophe.