Spreadsheet: 749382d1632765511-conditional-formatting-days-in-a-dynamic-calendar-calendar-sample
Sheet: Sheet1

 |  |  |  | 2021
 |  | January |  |  |  |  |  |  |  |  | February
 |  | 1900-01-01 00:00:00 |  |  |  |  |  |  |  |  | 1900-01-02 00:00:00
 | WEEK | SUN | MON | TUE | WED | THU | FRI | SAT |  | WEEK | SUN | MON | TUE | WED | THU | FRI | SAT
 |  |  | 2020-12-28 00:00:00 | 2020-12-29 00:00:00 | 2020-12-30 00:00:00 | 2020-12-31 00:00:00 | 2021-01-01 00:00:00 | 2021-01-02 00:00:00 |  |  |  | 2021-02-01 00:00:00 | 2021-02-02 00:00:00 | 2021-02-03 00:00:00 | 2021-02-04 00:00:00 | 2021-02-05 00:00:00 | 2021-02-06 00:00:00
 |  | 2021-01-03 00:00:00 | 2021-01-04 00:00:00 | 2021-01-05 00:00:00 | 2021-01-06 00:00:00 | 2021-01-07 00:00:00 | 2021-01-08 00:00:00 | 2021-01-09 00:00:00 |  |  | 2021-02-07 00:00:00 | 2021-02-08 00:00:00 | 2021-02-09 00:00:00 | 2021-02-10 00:00:00 | 2021-02-11 00:00:00 | 2021-02-12 00:00:00 | 2021-02-13 00:00:00
 |  | 2021-01-10 00:00:00 | 2021-01-11 00:00:00 | 2021-01-12 00:00:00 | 2021-01-13 00:00:00 | 2021-01-14 00:00:00 | 2021-01-15 00:00:00 | 2021-01-16 00:00:00 |  |  | 2021-02-14 00:00:00 | 2021-02-15 00:00:00 | 2021-02-16 00:00:00 | 2021-02-17 00:00:00 | 2021-02-18 00:00:00 | 2021-02-19 00:00:00 | 2021-02-20 00:00:00
 |  | 2021-01-17 00:00:00 | 2021-01-18 00:00:00 | 2021-01-19 00:00:00 | 2021-01-20 00:00:00 | 2021-01-21 00:00:00 | 2021-01-22 00:00:00 | 2021-01-23 00:00:00 |  |  | 2021-02-21 00:00:00 | 2021-02-22 00:00:00 | 2021-02-23 00:00:00 | 2021-02-24 00:00:00 | 2021-02-25 00:00:00 | 2021-02-26 00:00:00 | 2021-02-27 00:00:00
 |  | 2021-01-24 00:00:00 | 2021-01-25 00:00:00 | 2021-01-26 00:00:00 | 2021-01-27 00:00:00 | 2021-01-28 00:00:00 | 2021-01-29 00:00:00 | 2021-01-30 00:00:00 |  |  | 2021-02-28 00:00:00 | 2021-03-01 00:00:00 | 2021-03-02 00:00:00 | 2021-03-03 00:00:00 | 2021-03-04 00:00:00 | 2021-03-05 00:00:00 | 2021-03-06 00:00:00
 |  | 2021-01-31 00:00:00 | 2021-02-01 00:00:00 | 2021-02-02 00:00:00 | 2021-02-03 00:00:00 | 2021-02-04 00:00:00 | 2021-02-05 00:00:00 | 2021-02-06 00:00:00 |  |  | 2021-03-07 00:00:00 | 2021-03-08 00:00:00 | 2021-03-09 00:00:00 | 2021-03-10 00:00:00 | 2021-03-11 00:00:00 | 2021-03-12 00:00:00 | 2021-03-13 00:00:00
 | OR(C7=AGGREGATE(15,6,C7:C12/(MONTH(C$7:C$12)=MONTH(C$8)*(TEXT(C$7:C$12,"ddd")="WED")),1),C7=AGGREGATE(15,6,C$7:C$12/(MONTH(C$7:C$12)=MONTH(C$8)*(TEXT(C$7:C$12,"ddd")="WED")),3))
 |  | March |  |  |  |  |  |  |  |  | April
 |  | 1900-01-03 00:00:00 |  |  |  |  |  |  |  |  | 1900-01-04 00:00:00
 | WEEK | SUN | MON | TUE | WED | THU | FRI | SAT |  | WEEK | SUN | MON | TUE | WED | THU | FRI | SAT
 |  |  | 2021-03-01 00:00:00 | 2021-03-02 00:00:00 | 2021-03-03 00:00:00 | 2021-03-04 00:00:00 | 2021-03-05 00:00:00 | 2021-03-06 00:00:00 |  |  |  | 2021-03-29 00:00:00 | 2021-03-30 00:00:00 | 2021-03-31 00:00:00 | 2021-04-01 00:00:00 | 2021-04-02 00:00:00 | 2021-04-03 00:00:00
 |  | 2021-03-07 00:00:00 | 2021-03-08 00:00:00 | 2021-03-09 00:00:00 | 2021-03-10 00:00:00 | 2021-03-11 00:00:00 | 2021-03-12 00:00:00 | 2021-03-13 00:00:00 |  |  | 2021-04-04 00:00:00 | 2021-04-05 00:00:00 | 2021-04-06 00:00:00 | 2021-04-07 00:00:00 | 2021-04-08 00:00:00 | 2021-04-09 00:00:00 | 2021-04-10 00:00:00
 |  | 2021-03-14 00:00:00 | 2021-03-15 00:00:00 | 2021-03-16 00:00:00 | 2021-03-17 00:00:00 | 2021-03-18 00:00:00 | 2021-03-19 00:00:00 | 2021-03-20 00:00:00 |  |  | 2021-04-11 00:00:00 | 2021-04-12 00:00:00 | 2021-04-13 00:00:00 | 2021-04-14 00:00:00 | 2021-04-15 00:00:00 | 2021-04-16 00:00:00 | 2021-04-17 00:00:00
 |  | 2021-03-21 00:00:00 | 2021-03-22 00:00:00 | 2021-03-23 00:00:00 | 2021-03-24 00:00:00 | 2021-03-25 00:00:00 | 2021-03-26 00:00:00 | 2021-03-27 00:00:00 |  |  | 2021-04-18 00:00:00 | 2021-04-19 00:00:00 | 2021-04-20 00:00:00 | 2021-04-21 00:00:00 | 2021-04-22 00:00:00 | 2021-04-23 00:00:00 | 2021-04-24 00:00:00
 |  | 2021-03-28 00:00:00 | 2021-03-29 00:00:00 | 2021-03-30 00:00:00 | 2021-03-31 00:00:00 | 2021-04-01 00:00:00 | 2021-04-02 00:00:00 | 2021-04-03 00:00:00 |  |  | 2021-04-25 00:00:00 | 2021-04-26 00:00:00 | 2021-04-27 00:00:00 | 2021-04-28 00:00:00 | 2021-04-29 00:00:00 | 2021-04-30 00:00:00 | 2021-05-01 00:00:00
 |  | 2021-04-04 00:00:00 | 2021-04-05 00:00:00 | 2021-04-06 00:00:00 | 2021-04-07 00:00:00 | 2021-04-08 00:00:00 | 2021-04-09 00:00:00 | 2021-04-10 00:00:00 |  |  | 2021-05-02 00:00:00 | 2021-05-03 00:00:00 | 2021-05-04 00:00:00 | 2021-05-05 00:00:00 | 2021-05-06 00:00:00 | 2021-05-07 00:00:00 | 2021-05-08 00:00:00
 |  | May |  |  |  |  |  |  |  |  | June
 |  | 1900-01-05 00:00:00 |  |  |  |  |  |  |  |  | 1900-01-06 00:00:00
 | WEEK | SUN | MON | TUE | WED | THU | FRI | SAT |  | WEEK | SUN | MON | TUE | WED | THU | FRI | SAT
 |  |  | 2021-04-26 00:00:00 | 2021-04-27 00:00:00 | 2021-04-28 00:00:00 | 2021-04-29 00:00:00 | 2021-04-30 00:00:00 | 2021-05-01 00:00:00 |  |  |  | 2021-05-31 00:00:00 | 2021-06-01 00:00:00 | 2021-06-02 00:00:00 | 2021-06-03 00:00:00 | 2021-06-04 00:00:00 | 2021-06-05 00:00:00
 |  | 2021-05-02 00:00:00 | 2021-05-03 00:00:00 | 2021-05-04 00:00:00 | 2021-05-05 00:00:00 | 2021-05-06 00:00:00 | 2021-05-07 00:00:00 | 2021-05-08 00:00:00 |  |  | 2021-06-06 00:00:00 | 2021-06-07 00:00:00 | 2021-06-08 00:00:00 | 2021-06-09 00:00:00 | 2021-06-10 00:00:00 | 2021-06-11 00:00:00 | 2021-06-12 00:00:00
 |  | 2021-05-09 00:00:00 | 2021-05-10 00:00:00 | 2021-05-11 00:00:00 | 2021-05-12 00:00:00 | 2021-05-13 00:00:00 | 2021-05-14 00:00:00 | 2021-05-15 00:00:00 |  |  | 2021-06-13 00:00:00 | 2021-06-14 00:00:00 | 2021-06-15 00:00:00 | 2021-06-16 00:00:00 | 2021-06-17 00:00:00 | 2021-06-18 00:00:00 | 2021-06-19 00:00:00
 |  | 2021-05-16 00:00:00 | 2021-05-17 00:00:00 | 2021-05-18 00:00:00 | 2021-05-19 00:00:00 | 2021-05-20 00:00:00 | 2021-05-21 00:00:00 | 2021-05-22 00:00:00 |  |  | 2021-06-20 00:00:00 | 2021-06-21 00:00:00 | 2021-06-22 00:00:00 | 2021-06-23 00:00:00 | 2021-06-24 00:00:00 | 2021-06-25 00:00:00 | 2021-06-26 00:00:00
 |  | 2021-05-23 00:00:00 | 2021-05-24 00:00:00 | 2021-05-25 00:00:00 | 2021-05-26 00:00:00 | 2021-05-27 00:00:00 | 2021-05-28 00:00:00 | 2021-05-29 00:00:00 |  |  | 2021-06-27 00:00:00 | 2021-06-28 00:00:00 | 2021-06-29 00:00:00 | 2021-06-30 00:00:00 | 2021-07-01 00:00:00 | 2021-07-02 00:00:00 | 2021-07-03 00:00:00
 |  | 2021-05-30 00:00:00 | 2021-05-31 00:00:00 | 2021-06-01 00:00:00 | 2021-06-02 00:00:00 | 2021-06-03 00:00:00 | 2021-06-04 00:00:00 | 2021-06-05 00:00:00 |  |  | 2021-07-04 00:00:00 | 2021-07-05 00:00:00 | 2021-07-06 00:00:00 | 2021-07-07 00:00:00 | 2021-07-08 00:00:00 | 2021-07-09 00:00:00 | 2021-07-10 00:00:00