DEV: Fix moment warnings (PR #14482)

When start/end was missing the time component the string passed to moment() would have a space at the end. This was causing these warnings:

Deprecation warning: value provided is not in a recognized RFC2822 or ISO format. moment construction falls back to js Date(), which is not reliable across all browsers and versions. Non RFC2822/ISO date formats are discouraged. Please refer to for more info.