# How can I calculate 27 tropical/solar year since my birthdate?

Let's say I was born on 27th November 1993 at 03:15:15 AM. Is there any way I can calculate exact 27 tropical cycle since my birthdate/birthtime.

What date and what time it will be after exact 27 tropical years since my birthdate/birthtime?

Answer: Under reasonable assumptions, Thursday, November 26th at 4:11:28pm in the same time zone you were born. Assumptions:

• You are in the same time zone now as you were at birth, and there has been no change to "daylight time" or "summer time" that would effect November 26th or November 27th of 1993 or 2020

• There is no leap second added at the end of 30 Jun 2020. If a leap second IS added, the time above would be 4:11:27pm instead of 4:11:28pm

• The time of your birth was measured precisely to the second. Human birth usally takes more than one second, but using a precise time here for theoretical purposes is fine.

The Unix commands I used to determine this are below; note that I use "UTC", but it doesn't matter what time zone you're in, provided it remained consistent.

# set the timezone to a variant of UTC that includes leap seconds

setenv TZ /usr/share/zoneinfo/right/UTC

# how many seconds from the epoch was your birth

date -d '1993-11-27 03:15:15' +%s

# per http://hpiers.obspm.fr/eop-pc/models/constants.html the tropical
# year is 365.242190402 days long where day is defined as 86400s; this
# gives us a 27 year total of...

calc "365.242190402*86400*27"

# or 852036981.7697856 seconds; adding this to the second of your birth:

calc "754370133+852036981.7697856"

# answer: 1606407114.7697856; rounding + converting this back to regular time

date -d @1606407115

# answer is Thu Nov 26 16:11:28 UTC 2020