And just to show how annoying prepositions are in English, it is worth pointing out that for months and years we would use "in" so: May was the month in which I graduated and 1995 was the year in which I was born.

The date on which. With days and dates, we use 'on'. I will come on Wednesday. I will come on the 14th. Let me know the date on which you will come.

Native English teacher here. Let's swap English for Spanish. live:.cid.db875d0e13d4096c