Apologies if some of these have already been mentioned... I tried to limit this list to songs from 1990 or earlier.
"Years" songs:
Through The Years - Kenny Rogers
Year Of The Cat - Al Stewart
Years - Wayne Newton
I.G.Y. (What A Beautiful World) - Donald Fagen (IGY = International Geophysical Year)
As The Years Go By - Mashmakhan (LOVE that song thanks to hearing it on Canadian oldie stations)
"Time of day or week" songs:
The Morning After - Maureen McGovern
Mornin' Beautiful - Tony Orlando & Dawn
Tonight - Ferrante & Teicher (from West Side Story)
Tonight, I Celebrate My Love - Peabo Bryson & Roberta Flack
Let Me Love You Tonight - Pure Prairie League
Tomorrow Doesn't Matter Tonight - Starship
Afternoon Delight - Starland Vocal Band
Lonely Weekends - Charlie Rich
Lookout Weekend - Debbie Deb
Weekend In New England - Barry Manilow
Nights Are Forever Without You - England Dan & John Ford Coley
All Through The Night - Cyndi Lauper
Night - Jackie Wilson
Summer Nights - John Travolta & Olivia Newton-John
All Our Tomorrows - Eddie Schwartz
Yester-me, Yester-you, Yesterday - Stevie Wonder
I Saw Linda Yesterday - Dickey Lee
"Day of the week" songs:
Tuesday Afternoon - Moody Blues
A Sunday Kind Of Love - Jo Stafford and various others
Thank God It's Friday - Love & Kisses
Saturday Morning Confusion - Bobby Russell
Sunday Girl - Blondie
Sunday Morning Coming Down - Johnny Cash
"Season" songs:
Winter World Of Love - Engelbert Humperdinck
Hot Fun In The Summertime - Sly & The Family Stone
Spring Love - Stevie B.
It Might As Well Be Spring - Dick Haymes, Sinatra, various others
Summer Rain - Johnny Rivers
Spring Is Here - Frank Sinatra
Summertime Blues - Eddie Cochran; Alan Jackson
Summertime, Summertime - The Jamies
Summer Rain - Belinda Carlisle
Sweet Summer Lovin' - Dolly Parton