Birth Days and Sorting Through the Timeline

I have my old Excel timeline that I can post if folks are interested.

Absolutely!

I broke mine into accounting quarters, which I guess you could consider to be seasonal. Originally I did this in Excel, but obv that format was torched when I posted it elsewhere.

Here's what I had before; it's had a few things inserted into it from others that I'll leave in for the hell of it.

Q1 : January - March
Q2 : April - June
Q3 : July - September
Q4 : October - December

"Overlap" simply means around the end of one quarter/beginning of the next.

280
Q1: Rhaegar/Elia marry. Mama Martell still alive.
Q2:
Q3:
Q4: Rhaenys born. Elia begins bedrest ~6 mos.

281
Sarella Sand is born to Oberyn Martell and a Trader from the Summer Isles (from Wraith)
Quentyn Martell is born to Doran Martell (from Wraith)
Q1 - overlap: Elia recovered. Escorted through Kingswood/Hightower injured. Arianne meets Rhaenys (mentions holding the baby in her TWOW sample chapter - this could only have happened between 281 and early 282, before the war)
Q2 - overlap: KWB defeated. (Led by Arthur Dayne, as Hightower still recovering from wound.) Simon Toyne killed. Jaime knighted. Tywin still Hand, Cersei in KL.
Q3 - overlap: False Spring, Tourney at Harrenhal announced (late Q3). Tywin/Cersei return to the Rock. Lyanna crowned; Jaime made KG; Ashara Dayne "not long at court". NOTE: I believe Elia either made a trip to Dorne/met up with her Dornish family after Rhaenys' birth & Ashara returned to court with her at that time, OR Ashara was actually standing in for Elia at the time of the ambush.
Q4: Winter returns with a vengeance. Snow covers KL, Blackwater freezes.

282
Q1: Fires burn in KL, Rhaegar not there to see them. Elia and Baby Aegon on Dragonstone.
Q2: Brandon/Petyr duel after pending Cat marriage announced. Just shy of wedding day Brandon "heard the news about Lyanna" and leaves. Sam Tarly conceived.
Overlap: Brandon/Rickard go to KL and are killed. Aerys calls for heads.
Q3: Jon Arryn revolts. Ned betrothed to Cat. Lady Dustin married "not half a year" when Jon Arryn/Robert called banners -
Lord Ryswell had wanted to marry Barbrey to Brandon (probably because they were already shagging), but married her to Dustin instead after that no longer possible due to announcement of Brandon's wedding to Cat (a Q1 wedding announcement to Q3 banner-call is about 6-8 months - just about right for Ryswell to find Barbrey a quickie husband).
Overlap: Fighting already in Vale, Gulltown. Ned returns to Winterfell - Fisherman's Daughter. Battles of Ashford and Summerhall.
Randall Tarly has a victory for the Crown.
Q4: Margaery Tyrell conceived (has to be Q4 given her name day window - I'm assuming Mace returned to Highgarden briefly after Ashford to reform his vanguard to march south). Mace Tyrell's van marches to SE to begin siege. Rhaegar AWOL, JonConn named Hand. Ned gathers army, rides south.

283
Q1: Battle of the Bells, Rebel victory at Stoney Sept. Rhae Rhae still away. Arryn heir killed in battle. Ned returns to Riverrun, double wedding. Cat pregnant. JonConn exiled. Mama Martell dead/gone, Doran Martell now Prince of Dorne. Samwell Tarly born.
Q2: More fighting in south. Ned off at war, Rhaegar "returns from the south" and starts organizing Royal forces; Dornish marching up the Boneway.
Overlap: Trident. Rhaella supposedly conceives Dany. Margaery Tyrell born (late summer birthday, like August) - conceived before Mace left for Siege in late Q3/early Q4
Q3: Sack of King's Landing (this is ~one year from JA calling banners, consistent with text).   Jon Snow born, per positioning of his name day within the year (late summer/early fall).
Overlap: Robb born - A Cat POV mentions being safe at RR w/newborn Robb as city torn apart.  Siege at SE lifted (this is ~one year from Battle of Ashford, consistent with text - Davos confirms TWICE through POV in late summer/early fall 299 that his delivery of onions/fish was "16 years ago"; siege lifted shortly after)
Q4: Ned heads south, Tower of Joy. Robert tasks Stannis with taking Dragonstone, Stannis begins building fleet.

284
Q1: Ned's long return trip from Dorne
Overlap: Ned back at Winterfell (this is ~one year after marriage to Cat, consistent with text), Jon there too
Q2: Dany born (supposedly) during fierce summer storm
Q3: late in quarter, Willem Darry & children flee to Braavos
Overlap: Assault on Dragonstone (this is ~one year after lifting of Siege, consistent with text)
Q4: War over, Robert and Cersei to marry.



I am happy to provide my logic behind these calculations, if I can remember what it was at the time. I'm sure it was totally rock solid!

Pretty much. And GRRM has also gone the medieval route of "aging up" young children....look at his descriptions of 3yo Rickon and of all the stuff Rhaenys was noted to have done around the same age. Very "mature" for toddlers compared to the modern world, because more was expected of kids back then. All kids grew up faster, in a relative sense. So yes, at 1.5yo Aegon would have most certainly been walking and talking and eating solid food.

This weirdness with Aegon is what leads me to think that a) Aegon was not born when we think he was or b) Aegon is not Elia's child. Or both.

You are picking up what I'm putting down! My crazypants thought is that there wasn't as much of a baby swap as there was a baby steal.