`dates_tz_protocol`

Protocol for zone-aware date-time conversion using cached TZif data.

| Availability: | logtalk_load(dates_tz(loader))

| Author: Paulo Moura | Version: 1:0:0 | Date: 2026-04-08

| Compilation flags: | static

| Dependencies: | (none)

| Remarks: | (none)

| Inherited public predicates: | (none)

.. contents:: :local: :backlinks: top

Public predicates

.. index:: utc_to_local_tz/3 .. _dates_tz_protocol/0::utc_to_local_tz/3:

utc_to_local_tz/3 ^^^^^^^^^^^^^^^^^^^^^

Converts a UTC date-time to the civil local date-time in the named zone. Requires the zone to be present in the cached TZif data.

| Compilation flags: | static

| Template: | utc_to_local_tz(UTCDateTime,Zone,LocalDateTime) | Mode and number of proofs: | utc_to_local_tz(+compound,+atom,-compound) - one_or_error

.. index:: local_to_utc_tz/3 .. _dates_tz_protocol/0::local_to_utc_tz/3:

local_to_utc_tz/3 ^^^^^^^^^^^^^^^^^^^^^

Converts a civil local date-time in the named zone to UTC. This strict variant fails silently if the local time falls in a DST gap (non-existent time) or a DST fold (ambiguous time). Requires the zone to be present in the cached TZif data.

| Compilation flags: | static

| Template: | local_to_utc_tz(LocalDateTime,Zone,UTCDateTime) | Mode and number of proofs: | local_to_utc_tz(+compound,+atom,-compound) - zero_or_one_or_error

.. index:: local_to_utc_tz_with_resolution/4 .. _dates_tz_protocol/0::local_to_utc_tz_with_resolution/4:

local_to_utc_tz_with_resolution/4 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Converts a civil local date-time in the named zone to UTC using an explicit resolution mode for ambiguous or non-existent times. The resolution mode can be strict (fail unless exactly one interpretation), first (prefer the earliest valid interpretation), second (prefer the latest valid interpretation), or all (enumerate all valid interpretations). Requires the zone to be present in the cached TZif data.

| Compilation flags: | static

| Template: | local_to_utc_tz_with_resolution(LocalDateTime,Zone,ResolutionMode,UTCDateTime) | Mode and number of proofs: | local_to_utc_tz_with_resolution(+compound,+atom,+atom,-compound) - zero_or_more

.. index:: convert_zones/4 .. _dates_tz_protocol/0::convert_zones/4:

convert_zones/4 ^^^^^^^^^^^^^^^^^^^

Converts a civil local date-time in one zone to the civil local date-time in another zone. Uses strict interpretation: fails if the source local time is in a DST gap or fold. Requires both zones to be present in the cached TZif data.

| Compilation flags: | static

| Template: | convert_zones(LocalDateTime,FromZone,ToZone,ResultDateTime) | Mode and number of proofs: | convert_zones(+compound,+atom,+atom,-compound) - zero_or_one_or_error

.. index:: convert_zones_with_resolution/5 .. _dates_tz_protocol/0::convert_zones_with_resolution/5:

convert_zones_with_resolution/5 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Converts a civil local date-time in one zone to the civil local date-time in another zone using an explicit resolution mode for the source zone. The resolution mode is applied when the source local time is ambiguous or non-existent. Requires both zones to be present in the cached TZif data.

| Compilation flags: | static

| Template: | convert_zones_with_resolution(LocalDateTime,FromZone,ResolutionMode,ToZone,ResultDateTime) | Mode and number of proofs: | convert_zones_with_resolution(+compound,+atom,+atom,+atom,-compound) - zero_or_more

Protected predicates

(none)

Private predicates

(none)

Operators

(none)

.. seealso::

:ref:`dates_tz <dates_tz/0>`