Question ladies

When is a good time to check bbt? i was told by many to check every at the same time within 4 hours of sleep range , so that's what I've been doing , i made a post and someone asked why i track at night as if I'm not supposed to , i also realized I had the wrong thermometer to be tracking so i did order a correct one which won't be here until the 17th.. so can someone tell me what time I'm supposed to track bbt , I've been doing it every night at 4 am since i slept at 12 and it was in the 4 hour range.