January 21, 2030 (Monday) to January 27, 2030 (Sunday)
Week 4 of 2030 runs from January 21, 2030 (Monday) to January 27, 2030 (Sunday). This is the 4th week of the year according to the ISO 8601 standard, in which weeks start on Monday.
Jan 21 is a Monday. It is the first day of Week 4 of 2030.
Jan 27 is a Sunday. It is the last day of Week 4 of 2030.
Jan 21 is in Week 4 of 2030 according to ISO 8601.
Jan 27 is in Week 4 of 2030 according to ISO 8601.
Week 4 of 2030 runs from January 21, 2030 to January 27, 2030.
Week 4 of 2030 starts on January 21, 2030, the 21th day of 2030.
Yes, all 7 days of Week 4 of 2030 fall within 2030.
2030 has 52 weeks according to ISO 8601.