The 6 attribute spells appear to work ok, I can see the increase in the record window. However, the seventh is a mysterious "GA". A quick look at the spells table told me the acronym matches Guardian Angel. However, this doesn't appear to work. After dying while Day of the Gods is cast I still reappear with 1 HP and 0 gold. Am I missing something, or is this spell broken?

(Not that I really use Guardian Angel a lot, just want to make sure my spells work properly)

Do you use GOG version? I just rechecked it myself in GOG version to be sure, and it correctly applies following buffs: Lucky Day, Meditation, Precision, Speed, Power. To be totally sure I also checked Day of Protection and Hour of Power and neither had any GA effect.

Sometimes manually patched MM 6 causes all kind of weirdness (e.g., I had broken combat feedback line when tried to patch my original MM 6). GOG has all MM 6 patches applied correctly (it even has working Shadow Guild in Frozen Highlands, which was broken was one of the patches). Various Platinum, Millenia etc. releases of MM 6 come non-patched and might also cause such kind of bugs.

Yes, I'm using the GOG version, no patches.

If you right click on the spell, in the description it tells you that it should apply GA. The manual mentions it too. However it is not applied.

Ah, now I see. I suppose it is just another somewhat misleading tooltip like the one with Wizard Eye, and spell was slightly redesigned when actual tooltip was done. It doesn't look like bug other than misleading tooltip. Developers removed GA from Day of the Gods most likely for the reason that GA is almost useless and didn't fit concept of "Day of the Gods" as spell which increases all primary stats.