strftime％Z在时间和日期时间上的行为不同

Question

>> Time.now.strftime("%Z")
=> "CST"
>> DateTime.now.strftime("%Z")
=> "+08:00"
>> DateTime.new(2017, 2, 1, 17, 30, 0, "PST").strftime("%Z")
=> "-08:00"

So I want to print out the timezone name so I reached to strftime . However it behaves differently if I give a DateTime to it. Why is this the case? Does that mean I can't use DateTime.new to initialize an arbitrary time of a specific timezone?

Answer 1

You can set the time zone of a DateTime with in_time_zone :

DateTime.now.in_time_zone("Pacific Time (US & Canada)").strftime("%Z")

Time will automatically include a time zone if specified.

Answer 2

I've run into the same issue. This appears to be the cause:

• Time knows its time zone (and we can derive the offset from that)
• DateTime only knows its offset from UTC (which might be more than one time zone, because of inconsistent observance of Daylight Savings Time)

For example, right now both Phoenix, Arizona and San Francisco, CA are the same offset from UTC (-0700), but different time zones (MST, and PDT, respectively).