The best time is the morning of your missed period using your first urine, as the HCG concentration is highest then. Testing too early can give false negatives. If you get a faint line, repeat it after 48 hours.
I would suggest waiting at least until the first day of your missed period, or even 2 days after. I tested 4 days early and got a negative, which made me cry for hours, only to get a positive later. Save yourself the anxiety and wait!
Wait until your period is actually missed before testing. I kept up with my gentle walks and stretching while waiting for my test day, which my doctor said was perfectly fine. Don't stress your body with early testing.
For the most accurate result, wait until your period is missed by a few days. If you get a positive, please call your gynac to schedule an early scan and confirm the pregnancy safely.
Do it 1-2 days after your missed period, preferably in the morning. I celebrated my positive test with a giant plate of hot chole bhature! Sending you best wishes for a positive result.