Functions
bool	is_leap_year (int year)
	Check if a year is a leap year.

int	days_in_month (int year, int month)
	Get the number of days in a month.

int	__attribute__ ((noinline)) day_of_week(int year

	return ((h+6) % 7)

	if (remaining_secs< 0)

	while (days >=(dim=days_in_month(year, month)))

bool	skip_tz_name (const char *&p)
	Skip a timezone name (letters or <...> quoted format)

	while (out_month<=12)

bool	parse_dst_rule (const char *&p, DSTRule &rule)
	Parse a DST rule in format Mm.w.d[/time], Jn[/time], or n[/time].

	for (int m=1;m< month;m++)

	switch (rule.type)

int32_t	parse_offset (const char *&p)
	Parse an offset in format [-]hh[:mm[:ss]].

void	julian_to_month_day (int julian_day, int &month, int &day)
	Convert Julian day (J format, 1-365 not counting Feb 29) to month/day.

void	day_of_year_to_month_day (int day_of_year, int year, int &month, int &day)
	Convert day of year (plain format, 0-365 counting Feb 29) to month/day.

int	day_of_week (int year, int month, int day)
	Calculate day of week for any date (0 = Sunday) Uses a simplified algorithm that works for years 1970-2099.

void	epoch_to_tm_utc (time_t epoch, struct tm *out_tm)
	Convert epoch to year/month/day/hour/min/sec (UTC)

time_t	calculate_dst_transition (int year, const DSTRule &rule, int32_t base_offset_seconds)
	Calculate the epoch timestamp for a DST transition in a given year.

Variables
int int	month = 1

int int int	day

int	j = year / 100

int	h = (day + (13 * (month + 1)) / 5 + k + k / 4 + j / 4 - 2 * j) % 7

void struct tm *	out_tm

int32_t	remaining_secs = epoch % 86400

out_tm	tm_sec = remaining_secs % 60

out_tm	tm_min = remaining_secs % 60

out_tm	tm_hour = remaining_secs / 60

out_tm	tm_wday = static_cast<int>((days + 4) % 7)

int	year = days_to_year(days)

out_tm	tm_year = year - 1900

out_tm	tm_yday = static_cast<int>(days)

int	dim

out_tm	tm_mon = month - 1

out_tm	tm_mday = static_cast<int>(days) + 1

out_tm	tm_isdst = 0

void int &	out_month = 1

void int int &	out_day

return	days = days_to_year_start(year) + days_from_year_start(year, month, day)

time_t const DSTRule &	rule

time_t const DSTRule int32_t	base_offset_seconds

Function Documentation

◆ attribute()

time_t esphome::time::internal::__attribute__ ( (noinline) )

Definition at line 285 of file posix_tz.cpp.

◆ calculate_dst_transition()

time_t esphome::time::internal::calculate_dst_transition	(	int	year,
		const DSTRule &	rule,
		int32_t	base_offset_seconds )

Calculate the epoch timestamp for a DST transition in a given year.

Parameters

year	The year (e.g., 2026)
rule	The DST rule (month, week, day_of_week, time)
base_offset_seconds	The timezone offset to apply (std or dst depending on context)

Returns: Unix epoch timestamp of the transition

◆ day_of_week()

int esphome::time::internal::day_of_week	(	int	year,
		int	month,
		int	day )

Calculate day of week for any date (0 = Sunday) Uses a simplified algorithm that works for years 1970-2099.

◆ day_of_year_to_month_day()

void esphome::time::internal::day_of_year_to_month_day	(	int	day_of_year,
		int	year,
		int &	month,
		int &	day )

Convert day of year (plain format, 0-365 counting Feb 29) to month/day.

Parameters

	day_of_year	Day number 0-365
	year	The year (for leap year calculation)
[out]	month	Output: month 1-12
[out]	day	Output: day of month

◆ days_in_month()

int esphome::time::internal::days_in_month	(	int	year,
		int	month )

Get the number of days in a month.

Definition at line 59 of file posix_tz.cpp.

◆ epoch_to_tm_utc()

void esphome::time::internal::epoch_to_tm_utc	(	time_t	epoch,
		struct tm *	out_tm )

Convert epoch to year/month/day/hour/min/sec (UTC)

◆ for()

esphome::time::internal::for ( )

Definition at line 276 of file posix_tz.cpp.

◆ if()

esphome::time::internal::if ( )

Definition at line 91 of file posix_tz.cpp.

◆ is_leap_year()

bool esphome::time::internal::is_leap_year ( int year )

Check if a year is a leap year.

Definition at line 31 of file posix_tz.cpp.

◆ julian_to_month_day()

void esphome::time::internal::julian_to_month_day	(	int	julian_day,
		int &	month,
		int &	day )

Convert Julian day (J format, 1-365 not counting Feb 29) to month/day.

Parameters

	julian_day	Day number 1-365
[out]	month	Output: month 1-12
[out]	day	Output: day of month

◆ parse_dst_rule()

bool esphome::time::internal::parse_dst_rule	(	const char *&	p,
		DSTRule &	rule )

Parse a DST rule in format Mm.w.d[/time], Jn[/time], or n[/time].

Parameters

p	Pointer to current position, updated on return
rule	Output: the parsed rule

Returns: true if parsing succeeded

Definition at line 220 of file posix_tz.cpp.

◆ parse_offset()

int32_t esphome::time::internal::parse_offset ( const char *& p )

Parse an offset in format [-]hh[:mm[:ss]].

Parameters

p	Pointer to current position, updated on return

Returns: Offset in seconds

◆ return()

esphome::time::internal::return ( (h+6) % 7 )

◆ skip_tz_name()

bool esphome::time::internal::skip_tz_name ( const char *& p )

Skip a timezone name (letters or <...> quoted format)

Parameters

p	Pointer to current position, updated on return

Returns: true if a valid name was found

Definition at line 124 of file posix_tz.cpp.

◆ switch()

esphome::time::internal::switch ( rule. type )

Definition at line 296 of file posix_tz.cpp.

◆ while() [1/2]

esphome::time::internal::while ( days >= dim=days_in_month(year, month) )

Definition at line 114 of file posix_tz.cpp.

◆ while() [2/2]

esphome::time::internal::while ( out_month<= 12 )

Definition at line 186 of file posix_tz.cpp.

Variable Documentation

◆ base_offset_seconds

return days *rule time_seconds esphome::time::internal::base_offset_seconds

Initial value:

{

int month, day

month

uint8_t month

Definition date_entity.h:1

day

uint8_t day

Definition date_entity.h:2

Definition at line 293 of file posix_tz.cpp.

◆ day

static int int int esphome::time::internal::day

Initial value:

{
  
  if (month < 3) {
    month += 12;
    year--;
  }
  int k = year % 100

Definition at line 74 of file posix_tz.cpp.

◆ days

int64_t esphome::time::internal::days = days_to_year_start(year) + days_from_year_start(year, month, day)

Definition at line 279 of file posix_tz.cpp.

◆ dim

int esphome::time::internal::dim

Definition at line 113 of file posix_tz.cpp.

◆ h

int esphome::time::internal::h = (day + (13 * (month + 1)) / 5 + k + k / 4 + j / 4 - 2 * j) % 7

Definition at line 82 of file posix_tz.cpp.

◆ j

int esphome::time::internal::j = year / 100

Definition at line 81 of file posix_tz.cpp.

◆ month

static int int esphome::time::internal::month = 1

Definition at line 74 of file posix_tz.cpp.

◆ out_day

void int int int & esphome::time::internal::out_day

Initial value:

{
  
  int remaining = julian_day

Definition at line 180 of file posix_tz.cpp.

◆ out_month

void int int & esphome::time::internal::out_month = 1

Definition at line 180 of file posix_tz.cpp.

◆ out_tm

void struct tm* esphome::time::internal::out_tm

Initial value:

{
  
  int64_t days = epoch / 86400

Definition at line 87 of file posix_tz.cpp.

◆ remaining_secs

esphome::time::internal::remaining_secs = epoch % 86400

Definition at line 90 of file posix_tz.cpp.

◆ rule

time_t const DSTRule& esphome::time::internal::rule

Definition at line 293 of file posix_tz.cpp.

◆ tm_hour

out_tm esphome::time::internal::tm_hour = remaining_secs / 60

Definition at line 99 of file posix_tz.cpp.

◆ tm_isdst

out_tm esphome::time::internal::tm_isdst = 0

Definition at line 121 of file posix_tz.cpp.

◆ tm_mday

out_tm esphome::time::internal::tm_mday = static_cast<int>(days) + 1

Definition at line 120 of file posix_tz.cpp.

◆ tm_min

out_tm esphome::time::internal::tm_min = remaining_secs % 60

Definition at line 98 of file posix_tz.cpp.

◆ tm_mon

out_tm esphome::time::internal::tm_mon = month - 1

Definition at line 119 of file posix_tz.cpp.

◆ tm_sec

out_tm esphome::time::internal::tm_sec = remaining_secs % 60

Definition at line 96 of file posix_tz.cpp.

◆ tm_wday

out_tm esphome::time::internal::tm_wday = static_cast<int>((days + 4) % 7)

Definition at line 102 of file posix_tz.cpp.

◆ tm_yday

out_tm esphome::time::internal::tm_yday = static_cast<int>(days)

Definition at line 109 of file posix_tz.cpp.

◆ tm_year

out_tm esphome::time::internal::tm_year = year - 1900

Definition at line 108 of file posix_tz.cpp.

◆ year

void int esphome::time::internal::year = days_to_year(days)

Definition at line 107 of file posix_tz.cpp.

Functions

Variables

Function Documentation

◆ __attribute__()

◆ calculate_dst_transition()

◆ day_of_week()

◆ day_of_year_to_month_day()

◆ days_in_month()

◆ epoch_to_tm_utc()

◆ for()

◆ if()

◆ is_leap_year()

◆ julian_to_month_day()

◆ parse_dst_rule()

◆ parse_offset()

◆ return()

◆ skip_tz_name()

◆ switch()

◆ while() [1/2]

◆ while() [2/2]

Variable Documentation

◆ base_offset_seconds

◆ day

◆ days

◆ dim

◆ h

◆ j

◆ month

◆ out_day

◆ out_month

◆ out_tm

◆ remaining_secs

◆ rule

◆ tm_hour

◆ tm_isdst

◆ tm_mday

◆ tm_min

◆ tm_mon

◆ tm_sec

◆ tm_wday

◆ tm_yday

◆ tm_year

◆ year

◆ attribute()