To and From strings used with different meanings

The Thunderbird mockups Write window uses the To: and From: strings in the context of e-mail, as addresses.
The Shotwell mockup uses the same strings as the end points of a time range, from which the images are from.
To translate these words my language uses different words (think: Addressee and Sender vs Start and End), but these are present in the template only once, so it is impossible for me to properly localize them.

Normally, we use translation contexts to differentiate between the same strings with different meanings[1], but I have no idea how can this be implemented with HTML and the translate-html script. A trivial workaround could be to include a space after the colon in one set of the strings, that should make them different from gettext POV, yet it would have not much influence on the look of the original[2].

[1]: http://www.gnu.org/software/gettext/manual/gettext.html#Contexts
[2]: famous last words :)