Use UTC as the internal datetime format

homeassistant/util/dt.py

@@ -0,0 +1,99 @@
+"""
+homeassistant.util.dt
+~~~~~~~~~~~~~~~~~~~~~
+
+Provides helper methods to handle the time in HA.
+
+"""
+import datetime as dt
+
+import pytz
+
+DATE_STR_FORMAT = "%H:%M:%S %d-%m-%Y"
+UTC = DEFAULT_TIME_ZONE = pytz.utc
+
+
+def set_default_time_zone(time_zone):
+    """ Sets a default time zone to be used when none is specified. """
+    global DEFAULT_TIME_ZONE  # pylint: disable=global-statement
+
+    assert isinstance(time_zone, dt.tzinfo)
+
+    DEFAULT_TIME_ZONE = time_zone
+
+
+def get_time_zone(time_zone_str):
+    """ Get time zone from string. Return None if unable to determine. """
+    try:
+        return pytz.timezone(time_zone_str)
+    except pytz.exceptions.UnknownTimeZoneError:
+        return None
+
+
+def utcnow():
+    """ Get now in UTC time. """
+    return dt.datetime.utcnow().replace(tzinfo=pytz.utc)
+
+
+def now(time_zone=None):
+    """ Get now in specified time zone. """
+    if time_zone is None:
+        time_zone = DEFAULT_TIME_ZONE
+
+    return utcnow().astimezone(time_zone)
+
+
+def as_utc(dattim):
+    """ Return a datetime as UTC time.
+        Assumes datetime without tzinfo to be in the DEFAULT_TIME_ZONE. """
+    if dattim.tzinfo == pytz.utc:
+        return dattim
+    elif dattim.tzinfo is None:
+        dattim = dattim.replace(tzinfo=DEFAULT_TIME_ZONE)
+
+    return dattim.astimezone(pytz.utc)
+
+
+def as_local(dattim):
+    """ Converts a UTC datetime object to local time_zone. """
+    if dattim.tzinfo == DEFAULT_TIME_ZONE:
+        return dattim
+    elif dattim.tzinfo is None:
+        dattim = dattim.replace(tzinfo=pytz.utc)
+
+    return dattim.astimezone(DEFAULT_TIME_ZONE)
+
+
+def utc_from_timestamp(timestamp):
+    """ Returns a UTC time from a timestamp. """
+    return dt.datetime.fromtimestamp(timestamp, pytz.utc)
+
+
+def datetime_to_local_str(dattim, time_zone=None):
+    """ Converts datetime to specified time_zone and returns a string. """
+    return datetime_to_str(as_local(dattim))
+
+
+def datetime_to_str(dattim):
+    """ Converts datetime to a string format.
+
+    @rtype : str
+    """
+    return dattim.strftime(DATE_STR_FORMAT)
+
+
+def str_to_datetime(dt_str):
+    """ Converts a string to a UTC datetime object.
+
+    @rtype: datetime
+    """
+    try:
+        return dt.datetime.strptime(
+            dt_str, DATE_STR_FORMAT).replace(tzinfo=pytz.utc)
+    except ValueError:  # If dt_str did not match our format
+        return None
+
+
+def strip_microseconds(dattim):
+    """ Returns a copy of dattime object but with microsecond set to 0. """
+    return dattim.replace(microsecond=0)