Modern Chrono AddCalendarDays

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AddCalendarDays

Adds calendar days, keeping the same clock time across a DST change.

Syntax

AddCalendarDays( 1 )

Notes

• same wall-clock time tomorrow. Re-resolves the

Examples

#import "std/chrono"
using chrono

'' CALENDAR arithmetic: "same time tomorrow". It walks the civil date
'' and then re-resolves the offset, so the wall-clock time survives a
'' DST boundary -- where AddDays( 1 ), being exactly 86400 seconds,
'' would shift it by an hour.
dim as DateTime d = DateTime( 2026, 3, 7, 12, 0, 0, 0 )

print d.AddCalendarDays( 1 ).ToIsoString( )       '' 2026-03-08T12:00:00
print d.AddCalendarDays( -7 ).ToIsoString( )      '' 2026-02-28T12:00:00

'' With no offset attached there is nothing to re-resolve and the two
'' agree exactly
print d.HasOffset            '' false

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Library: Chrono Date and Time
Category: Date and Time (Chrono)
Documented under: Exact Arithmetic Vs Calendar Arithmetic