Q:

What time NPCs arrive at your town in Terraria once their requirements are met? 

The timing I believe is around morning when the Terraria NPCs arrival which requirements are met (I'm not sure about respawning).  But has anyone been keeping track on the exact time they arrive? 

A:

If its daytime it will usually will have 1 NPC every 2 Minutes. 
If its night time the NPCs will not spawn. 
However it also affects if a bloodmoon has happened.  If a Bloodmoon has occured the NPC will not spawn for the first 10 minutes of the day after. 
Officially Day starts 4:30 game time
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