How would you write a regular expression for describing valid dates in the format YYYY-MM-DD where under these SPECIFIC conditions: YYYY is a year after 1900 MM is a month DD is a day

I really want to under stand writing this is in regnex, but to know avail and still stuck on this result:

^\d{4}-(0[1-9]|1[0-2])-(0[1-9]|[12][0-9]|3[01])$

which is fine, but I struggle the read and properly implement the correct restrictions for this line, please help, and thank you.