This is what we know of SkC:
Leafstar, Sparrowpelt, Cherrytail, Macgyver, Fallowfern and Frecklewish all joined before TNP.
Tinycloud, Mintfur and Sagenose were kits when they joined in FQ.
Plumwillow, Rabbitleap and Nettlesplash were born before TNP.
Harrybrook was born in the TNP.
Hawkwing, Cloudmist and Blossomheart are the confusing ones. Cherrytail was pregnant in TNP, her kits were apprentices in OOTS and they became warriors after BrS. I headcanon that Cherrytail had another litter that died. That would be sad, but it would also make more sense. Aside from the becoming warriors pretty late thing.
Bellaleaf was around during OOTS (she was a kit when Ravenpaw first meets her) and again doesn't become a warrior until after BrS.
Tree was born after OOTS.
Fidgetflake became an apprentice when SkC was forced to leave the gorge, while Palesky, Gravelnose, Fringewhisker and Nectarsong were very young kits at this time.
Reedclaw, Dewspring, Violetshine, Quailfeather, Sunnypelt and Pigeonfoot were born during AVOS.
Kitescratch, Turtlecrawl, Rootspring, Needleclaw and Wrenpaw were born in between AVOS and TBC.
Beekit and Beetlekit were born during TBC.