Lenovo has started using the T14 name for the standard 14" ThinkPad T series in 2020, after calling it ThinkPad T4xx prior to that. So the 2020 ThinkPad T14 is the ThinkPad T14 Gen 1, followed by T14 Gen 2 in 2021, Gen 3 in 2022, Gen 4 in 2023, Gen 5 in 2024...

If you have a T14 at your hand, the bottom plate of the laptop should have the model name and generation imprinted on it. It should be also visible in Windows System Information app.

If you don't have any other way to find out the year of release or generation, the best way is to find its processor generation / series.

ThinkPad T14 Gen 1 2020 - 10th Gen Intel Core i5 / i7 10xxxU series or AMD Ryzen 5 / 7 4xxxU series.
ThinkPad T14 Gen 2 2021 - 11th Gen Intel Core i5 / i7 11xxxU series or AMD Ryzen 5 / 7 5xxxU series.
ThinkPad T14 Gen 3 2022 - 12th Gen Intel Core i5 / i7 12xxxU series or AMD Ryzen 5 / 7 6xxxU series.
ThinkPad T14 Gen 4 2023 - 13th Gen Intel Core i5 / i7 13xxxU series or AMD Ryzen 5 / 7 7xxxU series.
ThinkPad T14 Gen 5 2024 - Intel Core Ultra (without i prefix) 5 / 7 1xxU series or AMD Ryzen 5 / 7 8xxxU series.