2nd trimester

Melanie • Woman of God 🙏🏽 01/26/17 👧🏽💖 09/15/2020 👶🏽💙

I’m so confused when the second trimester starts. I’m currently 12 weeks and 5 days, ant I heard that the 2nd trimester starts at the beginning of 13 weeks but I also heard it starts at the beginning of 14 weeks. When does the 2nd trimester start?