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Fix date idate subtraction #7828

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Fix date idate subtraction #7828

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27bfb97
add fix
ben-schwen Jul 21, 2026
60af884
Merge branch 'master' into fix_date_idate_sub
ben-schwen Jul 23, 2026
0d1dfbc
reregister more
ben-schwen Jul 24, 2026
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19 changes: 11 additions & 8 deletions .ci/atime/tests.R
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Original file line number Diff line number Diff line change
Expand Up @@ -421,14 +421,17 @@ test.list <- atime::atime_test_list(
expr = {
ns = environment(data.table::as.IDate)
s3_table = get(".__S3MethodsTable__.", envir = baseenv())
if (exists("chooseOpsMethod.IDate", envir = s3_table)) {
rm("chooseOpsMethod.IDate", envir = s3_table)
}
if (exists("chooseOpsMethod.IDate", envir = ns, inherits = FALSE)) {
base::registerS3method(
"chooseOpsMethod", "IDate",
get("chooseOpsMethod.IDate", envir = ns),
envir = ns)
s3_generics = c("chooseOpsMethod.IDate" = "chooseOpsMethod", "-.IDate" = "-")
for (s3_method in names(s3_generics)) {
if (exists(s3_method, envir = s3_table, inherits = FALSE)) {
rm(list = s3_method, envir = s3_table)
}
if (exists(s3_method, envir = ns, inherits = FALSE)) {
base::registerS3method(
s3_generics[[s3_method]], "IDate",
get(s3_method, envir = ns, inherits = FALSE),
envir = ns)
}
}
outer(short_date, data.table::as.IDate(long_date), `-`)
}),
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2 changes: 2 additions & 0 deletions NEWS.md
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Expand Up @@ -62,6 +62,8 @@

13. `rbindlist()` (and therefore the `rbind()` method for `data.table`s) no longer raises an error upon encountering more than approximately 50000 columns in a list entry, [#7793](https://github.com/Rdatatable/data.table/issues/7793). The bug was introduced in `data.table` version 1.18.2.1. Thanks to @rickhelmus for the report and @aitap for the fix.

14. Subtracting an `IDate` from a `Date` is fast again by avoiding unnecessary conversion to `POSIXlt`/`POSIXct`, [#7825](https://github.com/Rdatatable/data.table/issues/7825). Thanks @gilesheywood for the report and @ben-schwen for the fix.

### Notes

1. {data.table} now depends on R 3.5.0 (2018).
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11 changes: 10 additions & 1 deletion R/IDateTime.R
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Expand Up @@ -111,7 +111,16 @@ chooseOpsMethod.IDate = function(x, y, mx, my, cl, reverse) inherits(y, "Date")

`-.IDate` = function(e1, e2) {
if (!inherits(e1, "IDate")) {
if (inherits(e1, 'Date')) return(base::`-.Date`(e1, e2))
if (inherits(e1, "Date")) {
if (inherits(e2, "Date")) {
#7825 avoid base::`-.Date` to avoid conversion from IDate to POSIXlt/POSIXct
ans = unclass(e1) - unclass(e2)
setattr(ans, "class", "difftime")
setattr(ans, "units", "days")
return(ans)
}
return(base::`-.Date`(e1, e2))
Comment on lines +115 to +122

@MichaelChirico MichaelChirico Jul 24, 2026 •
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Unnesting the longer expression might be nicer

Suggested change
if (inherits(e2, "Date")) {
#7825 avoid base::`-.Date` to avoid conversion from IDate to POSIXlt/POSIXct
ans = unclass(e1) - unclass(e2)
setattr(ans, "class", "difftime")
setattr(ans, "units", "days")
return(ans)
}
return(base::`-.Date`(e1, e2))
if (!inherits(e2, "Date")) return(base::`-.Date`(e1, e2))
#7825 avoid base::`-.Date` to avoid conversion from IDate to POSIXlt/POSIXct
ans = unclass(e1) - unclass(e2)
setattr(ans, "class", "difftime")
setattr(ans, "units", "days")
return(ans)

}
stopf("can only subtract from \"IDate\" objects")
}
if (storage.mode(e1) != "integer")
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