If any time you’re not completely sure, just say it out loud. “It’s” is a contraction and translates to “it is.”
For example, the following sentence…
“The website had a total of 635 unique visitors since it’s launch on May 1st, 2016.”
…translates into…
“The website had a total of 635 unique visitors since it is launch on May 1st, 2016.”
…which is incorrect and sounds off. This sentence on the other hand…
“It’s now time for us (TheCrema and willy) to move on and get a proper grant to improve this product even further.”
…translates into…
“It is now time for us (TheCrema and willy) to move on and get a proper grant to improve this product even further.”
…is correct and also sounds right when read aloud. The same goes with other contractions.