Just thought I would share an observation; Gysahl popped at 8am on the 1st, 11am on the 5th, and tonight it just popped at 8pm. Similar to what Patafix said above as well as other various reports of spawn times, I'm thinking the time is not random but cycles through set times to give exposure to different regions.

8am->11am->8pm->11pm->repeat

I'll try to see what happens on the 11th and post back here. All times are CST (GMT-6) and adjusted for the recent time change.