From 075cf69bc06ae45ace89546efbff438f2849c6a7 Mon Sep 17 00:00:00 2001
From: Curtis Vogt <curtis.vogt@gmail.com>
Date: Fri, 3 Apr 2020 13:19:32 -0500
Subject: [PATCH] Support `eps` on `TimeType` types (#31487)

* Support eps on TimeType types

* Add news
---
 NEWS.md                    |  1 +
 stdlib/Dates/src/types.jl  | 31 +++++++++++++++++++++++--------
 stdlib/Dates/test/types.jl |  3 +++
 3 files changed, 27 insertions(+), 8 deletions(-)

diff --git a/NEWS.md b/NEWS.md
index cb15f98beb1c3..a145cbb4c730f 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -137,6 +137,7 @@ Standard library changes
   arrays.
 
 #### Dates
+* The `eps` function now accepts `TimeType` types ([#31487]).
 
 #### Statistics
 
diff --git a/stdlib/Dates/src/types.jl b/stdlib/Dates/src/types.jl
index 9116b51a87eb7..d5eb7ca6e287b 100644
--- a/stdlib/Dates/src/types.jl
+++ b/stdlib/Dates/src/types.jl
@@ -374,17 +374,32 @@ calendar(dt::DateTime) = ISOCalendar
 calendar(dt::Date) = ISOCalendar
 
 """
-    eps(::DateTime) -> Millisecond
-    eps(::Date) -> Day
-    eps(::Time) -> Nanosecond
+    eps(::Type{DateTime}) -> Millisecond
+    eps(::Type{Date}) -> Day
+    eps(::Type{Time}) -> Nanosecond
+    eps(::TimeType) -> Period
 
-Returns `Millisecond(1)` for `DateTime` values, `Day(1)` for `Date` values, and `Nanosecond(1)` for `Time` values.
+Return the smallest unit value supported by the `TimeType`.
+
+# Examples
+```jldoctest
+julia> eps(DateTime)
+1 millisecond
+
+julia> eps(Date)
+1 day
+
+julia> eps(Time)
+1 nanosecond
+```
 """
-Base.eps
+Base.eps(::Union{Type{DateTime}, Type{Date}, Type{Time}, TimeType})
+
+Base.eps(::Type{DateTime}) = Millisecond(1)
+Base.eps(::Type{Date}) = Day(1)
+Base.eps(::Type{Time}) = Nanosecond(1)
+Base.eps(::T) where T <: TimeType = eps(T)::Period
 
-Base.eps(dt::DateTime) = Millisecond(1)
-Base.eps(dt::Date) = Day(1)
-Base.eps(t::Time) = Nanosecond(1)
 
 Base.typemax(::Union{DateTime, Type{DateTime}}) = DateTime(146138512, 12, 31, 23, 59, 59)
 Base.typemin(::Union{DateTime, Type{DateTime}}) = DateTime(-146138511, 1, 1, 0, 0, 0)
diff --git a/stdlib/Dates/test/types.jl b/stdlib/Dates/test/types.jl
index d4fe39d22a552..fefe14a20ec19 100644
--- a/stdlib/Dates/test/types.jl
+++ b/stdlib/Dates/test/types.jl
@@ -181,6 +181,9 @@ c = Dates.Time(0)
 @testset "DateTime traits" begin
     @test Dates.calendar(a) == Dates.ISOCalendar
     @test Dates.calendar(b) == Dates.ISOCalendar
+    @test eps(DateTime) == Dates.Millisecond(1)
+    @test eps(Date) == Dates.Day(1)
+    @test eps(Time) == Dates.Nanosecond(1)
     @test eps(a) == Dates.Millisecond(1)
     @test eps(b) == Dates.Day(1)
     @test eps(c) == Dates.Nanosecond(1)