My doctor gave the first TT/Tdap around the 2nd trimester and the next dose 4 weeks later. She said timing can vary depending on your past vaccination history, so the gynac decides the exact dates for you.
Dont worry about figuring it out yourself beta, the doctor schedules tetanus shots during your regular checkups, mostly second trimester. Just keep going for your visits on time.
Both my pregnancies the TT injections were given in the 2nd trimester, two doses about a month apart. Your gynac schedules it, so just follow what she writes in your card and dont skip the second one.
It's normally in the middle months, two shots spaced out. I just put the dates in my phone reminder so I didnt miss the second one between work. Ask your doc to mark them clearly.