According to http://www.tw-cabal.com/glossary.html#Extern:
A lot of things happen at Extern, so I thought I would list them here. (see Midnight too) I will put them in order of occurrence later. **There is a lot more to add, I'm still fleshing this out. If you see something I missed, let me know. -T 7/3/02
1) Check for players with different alignments in the same corp. Apply penalties if needed.
2) Fedspace is cleared of Nav Haz.
3) Empty ships in Fedspace are repo'd. (unless locked in tow. see tip #4)
4) Players are towed for Armament Violations. (having more than 100 figs in Fedspace while off-line)
5) Check for too many players in a Fedspace sector. (Random off-line players are towed if the number of allowed off-line players is exceeded in the sector) (not TOTALLY random
6) Reset Tax time.
7) Reset Grimy Trader Curse.
Recover deaths (2 pods).9) Reset Jettison Collies.
10) Reset Alignment loss for breaking into another corp.
11) Clear busts (if it's the right day. In MBBS mode, it happens here daily)
12) Player Figs and Mines are cleared out of MSL's. Planets with Cits in MSL's are reduced to LV 2 Cits.
13) Planets in overloaded sectors collide. Only 2 planets collide per extern.
14) Destroyed Class 0 and 9 ports rebuilt if the radiation is gone.
15) Nav Hazz clears/reduces
16) Port construction advances
17) Players and Corps timeout. Remaining assets go rougue.
and at midnight http://www.tw-cabal.com/glossary.html#Midnight:
A lot of things happen at midnight, so I thought I would list them here. (See Extern too)
1) Players that died the previous day are allowed back in. (no pod recovery, that happens at extern)
2) Hold, Fig, and Shield prices change at Class 0 and Class 9 ports
3) Players who log in after Midnight gain one point of Experience and one point of Alignment.
4) Citadel construction advances.
5) Underground wrong passwords resets.