Time difference in year between table datetime values and now

I have a vector of datetime values. I would like to get a vector of years elapsed between the datetime values and the present. How do I do this?

I tried

years(MyTable.BirthDate- now)

and got

Error using years
Input data must be a real, numeric array, or a duration array. Use YEAR to extract year numbers from a
datetime array.

I tried

year(MyTable.BirthDate- now)

but it rounded the values, and I would like the decimal difference. How can I get, for example, that one of the entries is 6.8 years old today?

Answer 1

[Steven Lord]

Don't use the now function. It returns a serial date number. Use datetime('now') (which returns a datetime) instead.

fiveYearsFromNow = datetime(2029, 5, 22)

fiveYearsFromNow = datetime
   22-May-2029

N = datetime('now')

N = datetime
   22-May-2024 21:18:40

y = years(fiveYearsFromNow-N)

y = 4.9970

But you may instead want to compute a calendarDuration instead of a duration. You can do this with the between function.

difference = between(N, fiveYearsFromNow) % Just shy of 5 years by timeofday(N)

difference = calendarDuration
   4y 11mo 29d 2h 41m 19.759s

To correct for the fact that fiveYearsFromNow represents midnight on May 22, 2029 you can add timeofday(N) to it so fiveYearsFromNow and N represent the same amount of time past midnight on their respective days.

T = timeofday(N)

T = duration
   21:18:40

difference = between(N, fiveYearsFromNow+T)

difference = calendarDuration
   5y