28 Sep 2018
Promo: Weekend Sale
Bug: The end date listed at announcement post is obviously wrong(September 30, 10pm UTC). The sale should end with the same-week Weekly Sale. The countdown clock at the promo page do match with Weekly Sale.

19 Oct 2018
Promo: (Let's call it a hidden Weekend Sale for now)
Bug: GOG made a bunch of games to have similar discounts, up to 75% off. But there are no any announcement about it.

GOG used to have many hidden sales [1], but this one looks like a Weekend Sale, not like a unannounced single promo.

[1] https://www.gog.com/forum/general/the_unannounced_gog_promo_thread

After a 4 hours delay, GOG announced the Weekend Sale.

22 Oct 2018
Promo: WEEKLY SALE: HOW DID I MISS THESE? - UP TO 80% OFF
Bug: Countdown clock of promo page is wrong. GOG should hire someone that know what is DST. They almost always mess up clocks during DST transition.

26 Oct 2018
Promo: Weekend Sale
Bug: Countdown clock of promo page is wrong. Exactly the same bug with the Weekly Sale, which is still not fixed.
GOG staff just do not know how to add or subtract.

Oct 2018
Promo: Trick or Treat Sale
Bug: Countdown clock on homepage is 6 hours short. The clock was not there initially. Over one day after the sale start, the clock appear under the Now on Sale tab, with a wrong countdown setting.
And no, the sale still have no standalone page. The countdown clock still link it to https://www.gog.com/games?tab=on_sale which also show other promo that are not part of Trick or Treat Sale

GOG make wrong clocks repeatedly, and GOG fanboys keep blame me for this.
I just can not realise why they can be so stupid.

Those two countdown clocks on homepage are fixed now. (They were three, but only two now.)
BUT, GOG have a very bad record to match their real discount and the display of countdown clocks.
While those clock showing are correct now, it is still possible that discounts disappear earlier.
If you want to buy games in this sale, please do not wait till last 6 hours before the end.

Party Hard has gone off sale. It was added late and ended early.
It definitely meet the Halloween theme, so it should not be one of the unannounced GOG promo.
Party Hard 2 is supposed to be discounted until November 4th, 4pm UTC. Why discount of Party Hard ended so early?
GOG is buggy as usual.

Nov 2018
Promo: Galactic Civilizations III – Star Control Heroes
Bug: Countdown clock is at least 2 days short. The announcement claimed that the promo will end on November 20th, 6pm UTC.

Nov 2018
Promo: https://www.gog.com/promo/20181119_weekly_sale
Bug: Fictorum OST was discounted initially, but got removed long before the promo end

Nov 2018
Promo: Frostpunk Endless Mode update
Bug: Countdown clock was wrong for about 5 days, but is fixed now.

Bug fixed.

12 Dec 2018
Promo: https://www.gog.com/promo/20181212_launch_promo_star_control_origins_dlc
Bug: Countdown clock is wrong

12 Dec 2018
Promo: https://www.gog.com/promo/20181212_launch_promo_monster_prom
Bug: Countdown clock is wrong