How to get the number out of a date?

General Usage
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1

I tried the below, it was able to generate the number I want, i.e., 730824, but how can I extract this number out?

My code:

using Dates
A = dump(Date(2001, 12, 5))

Results:

Date
  instant: Dates.UTInstant{Day}
    periods: Day
      value: Int64 730824

Thanks!

2

Maybe

julia> Date(2001, 12, 5).instant.periods.value
730824
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3 
julia> using Dates

julia> a = Date(2001,12,5)
2001-12-05

julia> Dates.value(a)
730824
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4

Both methods work! Many thanks, All.

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5

Note that this method will not work for all datetimes:

julia> using Dates

julia> d = now()
2021-10-25T22:39:14.665

julia> Dates.value(d)
63770884754665

julia> dump(d)
DateTime
  instant: Dates.UTInstant{Millisecond}
    periods: Millisecond
      value: Int64 63770884754665

The question is - to what resolution do you want this value? Relative to what, 01-01-1970? How do you get them and what do you want to do with them?

2 Likes
6

Thanks. I only need to have some loose idea, so precision to the day is more than enough. I have several decades of sampling data and I just want to see the date in the middle.

BTW, once I get the average datenumber, how do I convert it back to Date? I tried the below and it did not work well.

A = Date(2001,12,5);
B = Dates.value(A);  # get the date number
C = Dates.Date(B);   # Trying to convert the date number back to date.
7

I think you’re looking for unix2datetime and datetime2unix (which takes a DateTime). Julia has proper datetime arithmetic built in, so you should not have to work with the raw values.

Maybe you can explain what you want to do with them?

1 Like
8

I have several decades of sampling data. They have date information stored as 3 separate columns: Year, Month, and Day. What I need to find out is the average date.

9

Are you talking about the median, geometric or arithmetic mean…? How do you want to round, in case you don’t get an even integer (truncation, towards/away from zero, towards positive/negative infinity, …)?

Sorry if I come across as intrusive, it’s just hard for me to give a concrete suggestion when I’m not clear what you’re talking about :slight_smile:

10

No at all. I really appreciate your help.

My variables are changing smoothly with time. I want to find out the average date value so that I can adjust all data to that date. I think what I need is the arithmetic mean? I can round the results, so that shouldn’t be a problem. For this post, I just want to find out how to convert a date number like 730824 back to a date or its original Year, Monty and Day. Thanks.

11

You can use the Dates.UTD() function:

using Dates, Random
d = rand(Date(2021,10,1):Day(1):today(), 10)
d̄ = Date(Dates.UTD(round(Int, mean(Dates.value.(d)))))
2 Likes
12

It works like a charm! Thank you so much :+1:

1 Like