They were not announced on FB. FYI - you don't need a FB account to view those messages. (Some FB accounts do, not this one.) - https://www.facebook.com/ThroneKingdomAtWar/posts/
Another really good announce point is their Discord - https://discord.gg/rdyfTBT
Offers show timers in them as to when they expire. They were there, expiry time of 3d, and expired. And have been rolled over - they are present again.
Rolling over is typical for Holiday packs, say, for the week, e.g. Xmas, Easter, but you can't count on them / how log - beyond their expiry timer. Other special packs seem to be calendar / event rooted and you can't count on them being rolled over - e.g. Recent game update / battle packs. There also seem to be 'seasonal' packs, which seem to roll over for more than a few weeks. This seemed to be the case last year with 'Spring' packs that started before spring and went into summer - this may be the case with the current 'April' packs.
Here and now, the rolled over 'Holiday' (Seasonal?) packs seem to have names starting with / like 'April Discounts!'. I still see a 'Happy Holiday! Discount' pack. I though I saw a (Battle? / non-basic necessity) pack with 'Easter' in the title, I don't now - I may not have, 'Easter' not being a universal 'thing', and no point irritating or ignoring any particular group.
There are other similar 'Holiday'(?)-era packs on offer that seem more like a sale (that typically occurs around the same time), e.g. the current 'No Packs, No Gains' candle pack - 2x 500 candles of Ann, Lilian, and Sixtus.
[Get these, if you haven't already. Even, this time, buying reveals the same offer again the next day, rather than a much less generous repeat. 1,540 (IIRC) candles needed to max out - Lilian may be your thing, you want to max. out Sixtus to reduce study costs and times, and you will eventually want a maxed out Ann.]
Note that the US$19.99 packs give the most bang for your buck, at least on basic necessity RSS / Silver / Gold / Boosts that it is certain you will want an endless supply of.
Other sale packs of the moment include VIP, a duplicate 'April Discounts! Gold' pack (having boosts, unlike the other 'April Discounts! Gold' pack that only has gold), and Faith.
Your question is a good one, as other packs you want have a period to them, e.g. weekly Platinum, carts, or others every other or 3rd day - and combining the above with them is preferable, so your pack purchase cycle doesn't get reset for your obverse. Knowing these periods, and the expiry and/or rollover of the above helps one max their buying $.
In the #welcome-faq-rules on their Discord is also, if useful: