fix test, add note

JuliaInterop · Jul 18, 2024 · ad6314f · ad6314f
1 parent ca5bf98
commit ad6314f
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diff --git a/docs/src/conversions.md b/docs/src/conversions.md
@@ -84,6 +84,10 @@ r = reval("as.POSIXct('2020-10-09 12:09:46.1234')")
 d = rcopy(r)
 ```
 
+!!! note "Conversions to `DateTime` are given in UTC!"
+    `POSIXct` stores times internally as UTC with a timezone attribute.
+    The conversion to `DateTime` necessarily strips away timezone information, resulting in UTC values.
+
 ## DataFrames
 
 ```@example 1

diff --git a/src/convert/datetime.jl b/src/convert/datetime.jl
@@ -8,11 +8,12 @@ rcopy(::Type{DateTime}, s::Ptr{RealSxp}) = rcopy(DateTime, s[1])
 rcopy(::Type{Date}, x::Float64) = Date(Dates.UTInstant(Dates.Day((isnan(x) ? 0 : x) + 719163)))
 function rcopy(::Type{DateTime}, x::Float64)
     ms = ((isnan(x) ? 0 : x) + 62135683200) * 1_000
-    if !isinteger(ms)
+    ms_int = round(Int, ms)
+    if ms != ms_int
         @debug "Precision lost in conversion to DateTime"
     end
-    ms = round(Int, ms)
-    return DateTime(Dates.UTInstant(Millisecond(ms)))
+
+    return DateTime(Dates.UTInstant(Millisecond(ms_int)))
 end
 
 # implicit conversion `rcopy(d)`.

diff --git a/test/convert/datetime.jl b/test/convert/datetime.jl
@@ -136,8 +136,12 @@ r = RObject(d)
 @test rcopy(Array, r)[[1,3]] == d[[1,3]]
 @test ismissing(rcopy(Array, r)[2])
 
+# note that POSIXct stores times internaly as UTC, but assumes local
+# timezone information
+@test rcopy(R"as.POSIXct('2020-10-09 12:09:46', tz='UTC')") == DateTime("2020-10-09T12:09:46")
+
 # microseconds on R side #396
 @test_logs((:debug, "Precision lost in conversion to DateTime"),
             min_level=Logging.Debug,
             rcopy(R"as.POSIXct('2020-10-09 12:09:46.1234')"))
-@test rcopy(R"as.POSIXct('2020-10-09 12:09:46.1234')") == DateTime("2020-10-09T12:09:46.123")
+@test rcopy(R"as.POSIXct('2020-10-09 12:09:46.1234', tz='UTC')") == DateTime("2020-10-09T12:09:46.123")