Depending on your UV bulb brand, most only output UVB and UVA for 6-12 months. I recommend marking the date you start using the bulb somewhere so you can make sure you replace it when it’s running low. There are also UV test cards you can buy, but these won’t tell you whether it’s detecting UVA or UVB. I also agree with those who mentioned Reptifiles for care info, it’s a great resource that’s backed by science.