When is it the right time to meet his mother ?

I’ve known my boyfriend since HS and we’ve dated during HS and was on and off and we eventually moved on and 2014 we graduated. I dated someone for 2 years and we broke up in 2016 my boyfriend back from HS we started talking again and we hanged out , went on a couple dates. New Year’s Day we made it official and it’s almost gonna be a year together. We live 1-2 away from each and I’ve been at his house 2 times since we’ve been together. I’ve only meet his 23 year old sister and 6 year old sister. I still haven’t met his mother and I wonder if he’s not ready ?? How long did it take you lady’s to meet his mother ? How long would you wait or ask about it ?? I need advice please