my midwife tells me that the end of my first trimester is week 12. im 12 weeks 1 day. she says 2nd trimester begins at…

my midwife tells me that the end of my first trimester is week 12. im 12 weeks 1 day. she says 2nd trimester begins at week 13. but i am so lost because i see on the internet that week 13 is the end of first trimester and week 14 is the beginning of 2nd trimester. which one is correct??? im super confused.