extrapenguin

Novel-only, because I hate the donghua. Stuff might be off by a year.

-400 (time when Wen Mao, Lan An, and Baoshan Sanren were running around)
-350 (Lan Yi, Lan An's granddaughter, starts to exist around here)
-24 Qingheng-jun (assuming Lan Xichen born a year after wedding)
-21 Lan Qiren (assuming age gap of Lan Qiren & Qingheng-jun = that of Two Jades; could be as late as -18-ish)
-7 Nie Mingjue (this is just guesswork, but somewhere in this ballpark)
-3 Lan Xichen
-2 Jiang Yanli, Wen Chao (WC also maybe at -1)
-1 Jin Zixuan, Jin Guangyao (either exactly same age as Jin Zixuan or exactly one year younger)
00 Lan Wangji, Wei Wuxian, Jiang Cheng, Nie Huaisang
05 Xiao Xingchen, Song Lan
08 Xue Yang
10 Mo Xuanyu
12 A-Qing
15 (Wei Wuxian at the Cloud Recesses)
16 (Wei Wuxian wins archery competition at Discussion Conference)
17 (Sunshot Campaign starts)
18 Lan Sizhui; (Sunshot Campaign ends here or in 19)
19 rest of the juniors, maybe also Sizhui or Jin Ling
20 Jin Ling
21 (Wei Wuxian dies)
24 (Yueyang Cheng massacre)
26 (Xiao Xingchen dies)
34 (the present day)

Errata/notes:

Lan Xichen could also be at -2, in which case Qingheng-jun is at -23; Lan Qiren is unknown, but he's younger than his brother, though not too much (due to the responsibilities piling onto him so soon)
Jiang Cheng's and Wei Wuxian's parents are likely also born around -24
Nie Mingjue is guesswork, but he's significantly older than his brother, so roughly that ballpark
Wen Chao is 1-2 years older than Wei Wuxian, so -1 or -2
Song Lan is at 05 because someone willing to be friends with a 17-year-old is likely 17 as well
Xue Yang could be born in 06, 07, or 08, but it makes more sense for him to be as young as possible ie 08
the juniors are born 18-20, depending on stuff like what time of year it is and such, but that's an approximation that should fit
Lan Sizhui is 1-2 years older than Jin Ling, but whether either of them was born in 19 depends on the year cutoff
the Yi City timeline requires its own post, but Xiao Xingchen died pretty young
Jiang Cheng either is or was the youngest Sect Leader; if he is currently, then Jin Guangyao is older than him
the Sunshot Campaign can't have lasted over two years – more likely one – due to the crampedness of the post-Campaign timeline wrt Wei Wuxian's downfall