Julian way to do strptime?

General Usage
1

I’m converting an R script that uses strptime to extact datetime data from strings. Is there a more Julian way of doing this than calling Base.Libc.strptime?

I’m not very familiar with either string or date handling in Julia.

2

there is, what format specifiers occur in those uses of striptime? (show me a few examples, it is easier to explain how to do it in Julia with a few specific uses).

3

Sure:

Base.Libc.strptime.("SMAP_L4_SM_gph_%Y%m%dT%H%M%S", filenames)
4

Are all of the strings are prefixed with “SMAP_L4_SM_gph_” ?

(would 2018-May-17 at 22:18:05 be given as “SMAP_L4_SM_gph_20180517T221805”)

5 
using Dates

str = "SMAP_L4_SM_gph_20180517T221805"

# Define the format, `S` and `M` need to be escaped because they
# are format identifiers
df = dateformat"\S\MAP_L4_\S\M_gph_yyyymmddTHHMMSS"

DateTime(str, df)
# 2018-05-17T22:18:05
5 Likes
6

first, lets convert a string that only contains the date+time, given in that same pattern (yyyymmddTHHMMSS) where the “T” serves to separate the date part from the time part.

using Dates

myformat = dateformat"yyyymmddTHHMMSS"

str = "20180517T221805"

mydatetime = DateTime(str, muformat)

with that this happens

julia> mydatetime = DateTime(str, myformat)
2018-05-17T22:18:05

julia> Date(mydatetime), Time(mydatetime)
(2018-05-17, 22:18:05)
2 Likes
7

now lets suppose that all your date+time strings are prefixed by some (nonempty) character sequence that ends with ‘_’ (the [last] underscore in the string comes before the first digit of the year). This way you can have a slightly more general converter.

using Dates

myformat = dateformat"yyyymmddTHHMMSS"

strip_prefixed_chars(filenamestr) = split(filenamestr, '_')[end]

with that we can do this

julia> str = "SMAP_L4_SM_gph_20180517T221805"
"SMAP_L4_SM_gph_20180517T221805"

julia> mydatetime =  DateTime(strip_prefixed_chars(str), myformat)
2018-05-17T22:18:05
8

Ok dateformat string macro is the thing! so obvious I missed it.

Thanks!

9

But what if the string has a day-of-year? I couldn’t find a format that allows parsing, e.g.
“2021059T185321”

(many satellite products use variations of this to name their files)