core: now().timestamp() not returning correct value

Home Assistant release with the issue:

0.91.4

Last working Home Assistant release (if known): Unknown

Operating environment (Hass.io/Docker/Windows/etc.):

Hassio NUC image

Component/platform:

https://www.home-assistant.io/docs/configuration/templating/

Description of problem: The following two templates return the same value:

{{ utcnow().timestamp() }}
{{ now().timestamp() }}

1556243287.686556 1556243287.686613

These however do not return the same value:

{{ utcnow() }}
{{ now() }}

2019-04-26 01:48:07.686663+00:00 2019-04-26 11:48:07.686674+10:00

This has rendered my previously functional time templates incorrect and I now have to add my timezone offset in seconds to the now() timestamp.

Problem-relevant configuration.yaml entries and (fill out even if it seems unimportant):

Traceback (if applicable):

Additional information: