BACnetStack_SetTrendLogStartStopTime

bool BACnetStack_SetTrendLogStartStopTime(
  const uint32_t deviceInstance,
  const uint16_t objectType,
  const uint32_t objectInstance,
  const uint8_t startHour,
  const uint8_t startMinute,
  const uint8_t startSecond,
  const uint8_t startHundredthSecond,
  const uint8_t startYearMinus1900,
  const uint8_t startMonth,
  const uint8_t startDay,
  const uint8_t startWeekday,
  const uint8_t stopHour,
  const uint8_t stopMinute,
  const uint8_t stopSecond,
  const uint8_t stopHundredthSecond,
  const uint8_t stopYearMinus1900,
  const uint8_t stopMonth,
  const uint8_t stopDay,
  const uint8_t stopWeekday);

Sets the Start and Stop time properties of a Trend Log or Trend Log Multiple object.

This function should only be called after the AddTrendLogObject or AddTrendLogMultipleObject functions.

WHICH CLOCK: logging runs while Start_Time is unspecified or before “now” and Stop_Time is unspecified or after “now” (both strict). A bound counts as unspecified - it is ignored entirely - if ANY of its year, month, day, hour, minute, second or hundredths is 255, or its date is a pattern (month 13/14, day 32-34); only the weekday may be 255 in a concrete bound. The stack’s “now” is the CallbackGetSystemTime value (seconds since the Unix epoch, i.e. UTC) converted with gmtime and shifted by the Device object’s UTC_Offset as read through CallbackGetPropertySignedInteger (0 when the host does not serve UTC_Offset). Build the two values from that same clock - with UTC_Offset unserved, gmtime(time(NULL)), NOT localtime(). A window built from local time never brackets the stack’s “now” on a host outside UTC, and the log silently records nothing.

BACnet reference: ANSI/ASHRAE 135-2024 clause 12.25 (Trend Log Object Type).

Parameters

Parameter	Direction	Description
`deviceInstance`	in	The instance of the device that contains the Trend Log object.
`objectType`	in	The type of trend log object. Must be either BACnetObjectType::trendLog or BACnetObjectType::trendLogMultiple. With objectInstance, this is one BACnet Object Identifier carried as two parameters (see the API conventions).
`objectInstance`	in	The instance of the Trend Log object to update.
`startHour`	in	The hour for the start time. startHour through startWeekday together form Start_Time, a BACnetDateTime (cl. 12.25, 12.30, cl. 21); the stop parameters form Stop_Time the same way.
`startMinute`	in	The minute for the start time.
`startSecond`	in	The second for the start time.
`startHundredthSecond`	in	The hundredthSecond for the start time.
`startYearMinus1900`	in	The year for the start time. BACnet WIRE year, i.e. the calendar year MINUS 1900 (cl. 20.2.12) - 2026 is 126, not 2026. 255 = unspecified. This is a uint8_t: passing a 4-digit year truncates silently at the call site and produces a valid-looking wrong date.
`startMonth`	in	The month for the start time. January = 1 (cl. 20.2.12). 13 = odd months, 14 = even months, 255 = unspecified.
`startDay`	in	The day for the start time. 1..31 (cl. 20.2.12). 32 = last day of month, 33 = odd days, 34 = even days, 255 = unspecified.
`startWeekday`	in	The weekday for the start time. Monday = 1 .. Sunday = 7 (cl. 20.2.12). 255 = unspecified.
`stopHour`	in	The hour for the stop time.
`stopMinute`	in	The minute for the stop time.
`stopSecond`	in	The second for the stop time.
`stopHundredthSecond`	in	The hundredthSecond for the stop time.
`stopYearMinus1900`	in	The year for the stop time. BACnet WIRE year, i.e. the calendar year MINUS 1900 (cl. 20.2.12) - 2026 is 126, not 2026. 255 = unspecified. This is a uint8_t: passing a 4-digit year truncates silently at the call site and produces a valid-looking wrong date.
`stopMonth`	in	The month for the stop time. January = 1 (cl. 20.2.12). 13 = odd months, 14 = even months, 255 = unspecified.
`stopDay`	in	The day for the stop time. 1..31 (cl. 20.2.12). 32 = last day of month, 33 = odd days, 34 = even days, 255 = unspecified.
`stopWeekday`	in	The weekday for the stop time. Monday = 1 .. Sunday = 7 (cl. 20.2.12). 255 = unspecified.

Returns

True on success; false if the device or Trend Log object does not exist, or trending support was not compiled.

Topic: Schedules, calendars, trend logs and other object configuration. Declared in CASBACnetStackDLL.h.