JuliaLang/julia

[Dates] Time parsing is limited to millisecond precision

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#37,579 opened on Sep 15, 2020

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 (15 comments) (9 reactions) (0 assignees)Julia (5,773 forks)batch import
dateshelp wanted

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Description

I originally added this as a comment to #29339 but it deserves its own issue.

The parser in Dates is limited to parsing milliseconds even though Time and data types in other packages, e.g. AstroTime.jl, support higher precision.

julia> t = Time(12, 12, 12, 123, 456, 789)
12:12:12.123456789

julia> time_str = string(t)
"12:12:12.123456789"

julia> Time(time_str)
ERROR: InexactError: convert(Dates.Decimal3, 123456789)
Stacktrace:
 [1] tryparsenext at /Users/julia/buildbot/worker/package_macos64/build/usr/share/julia/stdlib/v1.5/Dates/src/io.jl:153 [inlined]
 [2] tryparsenext at /Users/julia/buildbot/worker/package_macos64/build/usr/share/julia/stdlib/v1.5/Dates/src/io.jl:41 [inlined]
 [3] macro expansion at /Users/julia/buildbot/worker/package_macos64/build/usr/share/julia/stdlib/v1.5/Dates/src/parse.jl:64 [inlined]
 [4] tryparsenext_core(::String, ::Int64, ::Int64, ::DateFormat{Symbol("HH:MM:SS.s"),Tuple{Dates.DatePart{'H'},Dates.Delim{Char,1},Dates.DatePart{'M'},Dates.Delim{Char,1},Dates.DatePart{'S'},Dates.Delim{Char,1},Dates.DatePart{'s'}}}, ::Bool) at /Users/julia/buildbot/worker/package_macos64/build/usr/share/julia/stdlib/v1.5/Dates/src/parse.jl:38
 [5] macro expansion at /Users/julia/buildbot/worker/package_macos64/build/usr/share/julia/stdlib/v1.5/Dates/src/parse.jl:150 [inlined]
 [6] tryparsenext_internal at /Users/julia/buildbot/worker/package_macos64/build/usr/share/julia/stdlib/v1.5/Dates/src/parse.jl:125 [inlined]
 [7] parse at /Users/julia/buildbot/worker/package_macos64/build/usr/share/julia/stdlib/v1.5/Dates/src/parse.jl:282 [inlined]
 [8] Time at /Users/julia/buildbot/worker/package_macos64/build/usr/share/julia/stdlib/v1.5/Dates/src/io.jl:524 [inlined] (repeats 2 times)
 [9] top-level scope at REPL[9]:1

Contributor guide

Research direction
Investigate the Dates.jl parsing code in io.jl and parse.jl to extend the fractional second parsing beyond millisecond precision. Look for the 'Decimal3' type and replace with a higher precision type. Ensure backward compatibility with existing formats.
Tech stack
julia
Domain
backend
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
3-5 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
JuliaDates module internals
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
40