Adds two convenience functions for later use.

infra/libs/time_functions/timestamp.py

Index: infra/libs/time_functions/timestamp.py
diff --git a/infra/libs/time_functions/timestamp.py b/infra/libs/time_functions/timestamp.py
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index 0000000000000000000000000000000000000000..2bda0a10638cb787c32abbad85e96942873055f3
--- /dev/null
+++ b/infra/libs/time_functions/timestamp.py
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+# Copyright 2015 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+
+"""Provides common timestamp functions."""
+
+import datetime
+import pytz
+
+
+def utctimestamp(dt):
+  """Converts a datetime object into a floating point timestamp since the epoch.
+
+  dt is the datetime to convert. If dt is a naive (non-tz-aware) object, it
+     will implicitly be treated as UTC.
+  """
+  epoch = datetime.datetime.utcfromtimestamp(0).replace(tzinfo=pytz.UTC)
+  # This check is from http://stackoverflow.com/a/27596917/3984761.
+  if dt.tzinfo is None or dt.tzinfo.utcoffset(dt) is None:
+    dt = dt.replace(tzinfo=pytz.UTC)
+  return (dt - epoch).total_seconds()
+
+
+def utcnow_ts():  # pragma: no cover
+  """Returns the floating point number of seconds since the UTC epoch."""
+  return utctimestamp(datetime.datetime.utcnow())