A more accurate response: 4 years, 5 months and 27 days. This duration was calculated from December 31, 2021 until today's date.
2021 was 4 years ago because we are now in 2026.
2021 was 53 months ago because we are now in June 2026. The math is simple: each year has 12 months, 4 x 12 = 48 and five months have passed since the beginning of 2026. So 48 + 5 = 53.
2021 was 234 weeks ago. The trick I like to use is to first calculate how many days have passed since 2021 and divide that number by 7 (days in a week). In short, 1639 / 7 = 234.14, but only the quotient is relevant here, 234.
2021 was 1639 days ago because today is June 28, 2026. This total comes from multiplying the number of years passed since 2021 (4) with the length of a standard year (365 days) for a base of 1460 days. Adding the 178 days that have passed in 2026 gives us 1638. However, we also must account for 1 leap year since 2021, which means 1638 + 1 = 1639.
As an academic exercise, it’s also possible to calculate how many hours passed since 2021. Given that we already know there are about 1639 days between then and now, we can multiply this number by 24 (the number of hours in a day) to get 39336 hours. Since it's currently 8:45 PM, we need to add the 20 hours that have passed since midnight to our subtotal of 39336. So 39336 + 20 = 39356, ergo 2021 was 39356 hours ago.
A lot happened in 2021. For a quick look at the most memorable events, here is the “The Year In Review 2021” cover from TIME Magazine.