dense.jinja

{% set _now = now() %}

======
quarter_ceil={{ _now - timedelta(microseconds=_now.microsecond, seconds=_now.second, minutes=_now.minute % 15) }}
quarter_floor={{ _now + timedelta(microseconds=-_now.microsecond, seconds=-_now.second, minutes=15-(_now.minute % 15)) }}
======
quarter_ceil+4h={{ _now - timedelta(microseconds=_now.microsecond, seconds=_now.second, minutes=_now.minute % 15, hours=-4) }}
quarter_floor+4h={{ _now + timedelta(microseconds=-_now.microsecond, seconds=-_now.second, minutes=15-(_now.minute % 15), hours=4) }}

pretty.jinja

{% set _now = now() %}

======
quarter_ceil={{ 
  _now - timedelta(
    microseconds=_now.microsecond, 
    seconds=_now.second, 
    minutes=_now.minute % 15
  ) 
}}
quarter_floor={{ _now + timedelta(
    microseconds=-_now.microsecond, 
    seconds=-_now.second, 
    minutes=15-(_now.minute % 15)
  ) 
}}
======
quarter_ceil+4h={{ 
  _now - timedelta(
    microseconds=_now.microsecond, 
    seconds=_now.second, 
    minutes=_now.minute % 15, 
    hours=-4
  ) 
}}
quarter_floor+4h={{ _now + timedelta(
    microseconds=-_now.microsecond, 
    seconds=-_now.second, 
    minutes=15-(_now.minute % 15), 
    hours=4
  ) 
}}