Handling browser-local datetimes in the present moment

The reason that we can't generally use JavaScript's built-in Date constructor at Tidepool—particularly when dealing with diabetes device data—is because JavaScript's Date only handles two types of datetime objects:

• browser-local datetimes (i.e., datetimes in the timezone that the browser detects the user is in)
• UTC datetimes

Since Tidepool generally deals with diabetes device datetimes in a user's configured, arbitrary timezone, JavaScript's Date does not provide the required functionality, and Moment.js must be used instead.

In the case of handling browser-local datetimes in the present moment, however, JavaScript's Date provides exactly what is needed^a: a browser-local "now."

For formatting a browser-local datetime, any tool may be used. @jebeck—and anyone else who has extensive experience with the strftime datetime-formatting API—may prefer d3-time-format over Moment^b.

^a. Assuming, of course, that the user does not do something pathologically silly, like manually configure their computer to a different timezone that their geographically current timezone. ↩

^b. @jebeck also think it is handy to use different libraries to help distinguish the very different requirements of handling diabetes device datetimes in an arbitrary timezone versus browser-local nows. ↩