The documentation has been expanded (the site will be updated when the next version is released).
localization.infoDates
Date and time formats used to display the selected time range in the header of the info popup.
moment.js - Display / Format
localization.infoDates.majorTimeFormats, localization.infoDates.minorTimeFormats
The formats used for the major unit when displaying a time range where the major unit is the same, for example, the selection contains multiple days from the same week.
If the display unit is days, the resulting header text is shown as
minorTimeFormats.d(from) - minorTimeFormats.d(to) majorTimeFormats.d(from)
, e.g. Feb 24 - Feb 26 2016
.
localization.infoDates.fullTimeFormats
The formats used when only a single time unit has been selected or when the selection spans multiple major units (for example, selecting days from multiple months).