How to convert years to days (in the past)?

Question

I want convert years to days (in the past) with a Linux command. For example:

1. The user give number: 10 years ago

2. The program should calculate the sum of the days in 10 years ago (ex: 10*12*31 (years/month/days) --> 3720 days).

3. The program sum it with current days from begin this year (ex: 3720 + 223) and return it.

Answer 1

这将为您提供一年的日期，即距现在的10年：

date -d '+10 years' +"%j"

Answer 2

The current time in seconds since 1970/01/01 (The Unix 'day 1'):

dnow=$(date +"%s")

The time exactly 10 years ago:

dthen=$(date -d '-10 years' +"%s")

Calculate today's day in the year:

dity=$(date +"%j")

Then just subtract one from the other, divide by the number of seconds in a day, and add today's day-in-the-year:

timespan=$(( (dnow - dthen) / (24*60*60) + dity ))

You should set $dnow after $dthen , to avoid an off-by-one error.

I'm not sure why anyone would want to do this, so if I've misinterpreted your question, please come back to us.