When is "Pi Day" ? annual observance - special deals at pie-making restaurants / franchise eating establishments

 The day of March 14 (annually)

since in decimal notation 

the exact amount of the

mathematical ratio called Pi

is 

3.1415926535 - - continues on and on

______________________________

3-14 - 2026

is a Saturday and that should be a

great day to enjoy of slice of

dessert pie

or 

main course pie such as quiche

or even

Pizza Pie of all sorts