Formats and Timezones

Formats and timezones

Summary

A format controls how a value is read or displayed; it is not the same as timestamp meaning or timezone conversion. Choose a field type first. Both input and output offer relevant presets plus an editable Custom choice near the top.

Date/time and ISO presets

For DateTime, common extended forms appear before compact forms. Date-only and Time-only lists retain their own relevant presets; numeric/text lists do not offer date/time presets.

Meaning	Extended example	Compact example
UTC datetime	2026-09-15T01:02:03Z	20260915T010203Z
Datetime with offset	2026-09-15T01:02:03+05:30	20260915T010203+0530
Date with hour/minute	2026-09-15T01:02	20260915T0102
Date with full time	2026-09-15T01:02:03	20260915T010203

GDTT masks use yyyy for year, MM for month, dd for day, HH for 24-hour, mm for minute and ss for second. Quoted 'T'/'Z' are shown explicitly; XX is a compact offset and XXX is colon-separated. Exact new ISO masks also work in Custom. These new profiles require GDTT 0.10.1 or later.

Z means actual UTC. UTC output converts an aware instant, including any date rollover. Example: 2026-01-01T01:02:03+05:30 becomes 2025-12-31T19:32:03Z. It never simply adds Z to an unknown local clock time. UTC/offset output blocks when the source timezone is unknown.

For naive local input, select its no-zone input format, configure the source timezone and a target timezone before exporting. Minute formats omit seconds; no-zone formats omit the offset. Choose those only when that information loss is intended. Existing millisecond and regional presets remain available.

Numeric formatting and decimal separators

• 0.00 is the common preset: 1.2345 becomes stored/exported 1.23 by default.
• #,##0.00 adds thousands grouping; 0, 0.000, 0.### and supported custom masks are available.
• Input formatting parses values without rounding them.
• Keep full numeric precision preserves the underlying number; preview and Excel formatting can show fewer decimals. CSV retains the available number in this mode. Earlier arithmetic rounding cannot be undone.
• Input/output decimal separators are separate dot/comma choices. For 1.234,56, use grouped input #,##0.00 and comma decimal. Do not rely on guessing.
• CSV remains comma-delimited; decimal-comma values are quoted. Excel separators follow Excel/OS regional settings. Excel's native numeric precision limits still apply.

Other Custom formats

Text supports @ or pre-{value}-post. Boolean supports True|False, Yes|No, 1|0 or two custom labels. Date/time examples include dd/MM/yyyy and yyyy-MM-dd HH:mm:ss. Quote literal words.

Custom is a documented subset, not the complete Excel mask language: arbitrary currency/scientific/percentage, conditional-color, multi-section and custom fractional-second masks are not promised. Invalid masks are reported instead of executed.

Timezone choices and meaning

Priority choices are UTC, Asia/Colombo (+05:30), Custom, half-hour offsets and the installed IANA list. Other valid minute offsets, such as +05:45, can be typed. Named regions retain historical/daylight-saving rules; fixed offsets never acquire DST rules.

Timezone conversion preserves an instant. Time Shift intentionally moves it and is a separate operation. Source timezone, reporting/boundary timezone and start/mid/end timestamp role are separate concepts. Ambiguous or nonexistent DST-local times require explicit handling or block.

Split / Join uses its own ISO or Python strptime input controls; do not paste Excel-style masks into a Python-pattern field. See its guide.

Source: Formatting and appearance.