Use UTC for meeting time or at least specify if it is the daylight saving time

[bact]

Every March/April and October/November, people in timezones that observe daylight savings are facing 1-2 weeks of meeting disruptions due to time confusion.

This occurs because the 1-hour forward/backward in parts of the world are not necessary happen at the same time.

For example, it used to be the case that North/Central America and Europe are quite in-sync in terms of daylight saving time (DST) schedule. But since 2007, thanks to the US Energy Policy Act of 2005 that extended DST in the US, this is no longer the case:

• EU DST starts in Last Sunday in March, while US DST starts earlier in Second Sunday in March
• EU DST ends in Last Sunday in October, while US DST ends later in First Sunday in November

ref: https://en.wikipedia.org/wiki/Daylight_saving_time_by_country#Scheduled_observance

As a project with international participants, may be it's best to stay neutral and reduce confusion by using UTC time.

The down side of this proposal is that North and Central American people may have to adjust.

At the very least, we should use either "US Eastern Standard Time" or "US Easter Daylight Time" to make the time fixed and not "float". (See PR #891)

If this change is not possible for any reason, we may like to add some notes to the README of these timezone nuance.