When to test if af doesn't show

I've been ttc a year now. My cycles were every 35 days but changed in April to every 31 days. Last month It came on cycle day 31 around 5pm. Today is day 31 & nearly 7pm. But still no af i really don't want to get my hopes up because my body has always played tricks on me:( it will probs come tonight or tomorrow but just wondering if it doesn't when to test? Thankyou