UTC Time Offset

Question

Really confused about the meaning of offset in email headers.

Header date reads as:

Sat, 8 Jun 2019 11:45:15 −0500

Does the time shown 11:45:15 is the actual time at timezone -0500

OR

Actual time at time zone -0500 is calculated by subtracting offset??

Thanks.

Answer 1

The timestamp you are seeing is the time in the given timezone using the given offset from UTC. The specific format of the timestamp you are looking at is an RFC2822 formatted timestamp which means that it follows a standard

Time: 11:45:15

Offset from UTC: −0500

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From RFC2822 spec:

   The zone specifies the offset from Coordinated Universal Time (UTC,
   formerly referred to as "Greenwich Mean Time") that the date and
   time-of-day represent.  The "+" or "-" indicates whether the
   time-of-day is ahead of (i.e., east of) or behind (i.e., west of)
   Universal Time.  The first two digits indicate the number of hours
   difference from Universal Time, and the last two digits indicate the
   number of minutes difference from Universal Time.  (Hence, +hhmm
   means +(hh * 60 + mm) minutes, and -hhmm means -(hh * 60 + mm)
   minutes).  The form "+0000" SHOULD be used to indicate a time zone at
   Universal Time.  Though "-0000" also indicates Universal Time, it is
   used to indicate that the time was generated on a system that may be
   in a local time zone other than Universal Time and therefore
   indicates that the date-time contains no information about the local
   time zone.

   A date-time specification MUST be semantically valid.  That is, the
   day-of-the-week (if included) MUST be the day implied by the date,
   the numeric day-of-month MUST be between 1 and the number of days
   allowed for the specified month (in the specified year), the
   time-of-day MUST be in the range 00:00:00 through 23:59:60 (the
   number of seconds allowing for a leap second; see [STD12]), and the
   zone MUST be within the range -9959 through +9959.

Answer 2

It simply means what is the difference between that time zone and the Greenwich mean time. Ex- UTC of India is +5.5