When is the length of the shadow equal to your height? Can someone give me a formula based on latitude?

Can someone give me a formula to find out when will your shadow be equal to the length of your height? I need to know this formula which concerns latitude in the Northern Hemisphere(a formula for the Southern Hemisphere would also be helpful) and the specific time which when used will help find when the length of your shadow be equal to your height? Please help! Thanks if you took the time to read this!!!!!