`fromdateiso8601` doesn't support the "decimal fraction" component in time values.

[slippycheeze]

Describe the bug
The ISO8601 time format supports a decimal fraction attached to the smallest component present; this is passably common for seconds to represent micro- or nano-seconds. Technically this is also applicable to the minute and hour components, though I have never seen that used in the wild.

fromdateiso8601 doesn't handle fractional seconds, which is an annoyance since I have several JSON applications that emit them, and where I'd like to do some date comparisons.

To Reproduce

] jq -nr '"2020-12-11T01:00:52.605001Z" | fromdateiso8601'
jq: error (at <unknown>): date "2020-12-11T01:00:52.605001Z" does not match format "%Y-%m-%dT%H:%M:%SZ"

Expected behavior
jq(1) would parse fractional seconds; ideally, it would also carry and emit them, but just ignoring the fraction would be sufficient for my needs.

Environment (please complete the following information):

• macOS 10.15.7 x64
• jq-1.6

Additional context
This is definitely an extension on the basic POSIX time functions, so perhaps isn't interesting to jq. I'd hope it was, since they are fairly commonly used, but I understand if this is bounced as "not interested".

[ecarlseen]

Having this issue also (MacOS 11.2.3, jq 1.6). It is rejecting my fractions.

[mbierman]

Is there any solution to this yet? I have a date like "1649333768.581" that I need to compare.

[yaningo]

Only workaround I found for now is to truncate the date and add the Z.

So the example of the initial issue description would be:

jq -nr '"2020-12-11T01:00:52.605001Z" | .[0:19] +"Z" | fromdateiso8601'

Not the most elegant, but it works ¯\_(ツ)_/¯

[jcmorrow]

FWIW https://github.com/01mf02/jaq handles this correctly.

[praetp]

No update on this ?

[wader]

@praetp have a look at #1409 for a summary of the situation

[wader]

btw gojq can parse fractions using %f:

$ gojq -nr '"2020-12-11T01:00:52.605001Z" | strptime("%Y-%m-%dT%H:%M:%S.%f%z") | mktime'
1607648452.605001

don't think there is any way to parse fractions optionally but a workaround could be to do something like:

# override fromdateiso8601 with own version that has fallback
$ gojq -nr 'def fromdateiso8601: strptime("%Y-%m-%dT%H:%M:%S%z")? // strptime("%Y-%m-%dT%H:%M:%S.%f%z") | mktime; "2020-12-11T01:00:52.605001Z", "2020-12-11T01:00:52Z" | fromdateiso8601'
1607648452.605001
1607648452

[Gitoffthelawn]

Only workaround I found for now is to truncate the date and add the Z.

So the example of the initial issue description would be:

jq -nr '"2020-12-11T01:00:52.605001Z" | .[0:19] +"Z" | fromdateiso8601'

Not the most elegant, but it works ¯_(ツ)_/¯

That works well. For people that like variety in their unpleasing workarounds, here is the technique I've been using that utilizes sub:

jq -nr '"2020-12-11T01:00:52.605001Z" | sub("\\.[0-9]+"; "") | fromdateiso8601'

It works too.

Six of one "meh", half a dozen of another. ;)

[jedvardsson]

Here is a workaround that doesn't truncate:

# util.jq
def fromdateiso8601fs:
    (
      capture("^(?<dt>.+)(?<fs>\\.\\d+)Z$")
      | .dt += "Z"
      | .fs |= tonumber
    ) // {dt: .}
    | (.dt|fromdateiso8601) + .fs
;

It parses date time without fractions and adds the fractions back on. Call it like so:

$ echo '["2025-03-11T18:13:42.123Z", "2025-03-11T18:13:42Z"]'|jq -L util.jq 'include "util"; .[]|fromdateiso8601fs'
1741716822.123
1741716822

Or as a oneliner:

echo '["2025-03-11T18:13:42.123Z", "2025-03-11T18:13:42Z"]' |jq 'def fromdateiso8601fs: (capture("^(?<dt>.+)(?<fs>\\.\\d+)Z$")|.dt += "Z"|.fs |= tonumber) // {dt: .}| (.dt|fromdateiso8601) + .fs;.[] |fromdateiso8601fs'
1741716822.123
1741716822