RADIUS attribute from rfc2869

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Event-Timestamp

This attribute is included in an Accounting-Request packet to
      record the time that this event occurred on the NAS, in seconds
      since January 1, 1970 00:00 UTC.

   A summary of the Event-Timestamp attribute format is shown below.
   The fields are transmitted from left to right.0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Type      |    Length     |             Value
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
              Value (cont)         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type

      55 for Event-Timestamp

   Length

      6

   Value

      The Value field is four octets encoding an unsigned integer with
      the number of seconds since January 1, 1970 00:00 UTC.

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