# Unexpected result for \`diff\` over DateTime range

**URL:** <https://discourse.julialang.org/t/unexpected-result-for-diff-over-datetime-range/86203>\
**Category:** General Usage\
**Tags:** bug\
**Created:** [August 23, 2022, 3:06pm UTC](https://discourse.julialang.org/t/unexpected-result-for-diff-over-datetime-range/86203 "2022-08-23T15:06:23Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![ohmsweetohm1](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/ohmsweetohm1/32/49126_2.png) [@ohmsweetohm1](https://discourse.julialang.org/u/ohmsweetohm1)\
**Post date:** [August 23, 2022, 3:06pm UTC](https://discourse.julialang.org/t/unexpected-result-for-diff-over-datetime-range/86203/1 "2022-08-23T15:06:23Z")

</div>

Consider the following:

```julia
julia> range = Dates.DateTime(2019):Dates.Year(1):Dates.DateTime(2020)
Dates.DateTime("2019-01-01T00:00:00"):Dates.Year(1):Dates.DateTime("2020-01-01T00:00:00")

julia> diff(range)
1-element Vector{Dates.DateTime}:
 0001-12-31T00:00:00

julia> diff(collect(range))
1-element Vector{Dates.Millisecond}:
 31536000000 milliseconds

```

The output for `diff(::AbstractRange)` seems wrong in this case.

---

<div class="post-metadata">

**Author:** ![jling](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/jling/32/212909_2.png) [@jling](https://discourse.julialang.org/u/jling)\
**Post date:** [August 23, 2022, 3:07pm UTC](https://discourse.julialang.org/t/unexpected-result-for-diff-over-datetime-range/86203/2 "2022-08-23T15:07:08Z")

</div>

Please use the latest Julia version (1.8.0)

```julia
julia> a = Dates.DateTime("2019-01-01T00:00:00"):Dates.Year(1):Dates.DateTime("2020-01-01T00:00:00")
DateTime("2019-01-01T00:00:00"):Year(1):DateTime("2020-01-01T00:00:00")

julia> diff(a)
1-element Vector{Millisecond}:
 31536000000 milliseconds

```