Transmission Date & Time
What it is
MMDDhhmmss in UTC/GMT — when the message entered the network. Used with DE 11 to match responses and reversals.
DE 7 is set when the message is transmitted and, unlike DE 12/13, is expressed in UTC. Together with DE 11 (STAN) and the acquirer/terminal identifiers it forms the practical matching key for responses, reversals, and duplicate detection.
Example values
0801143205August 1st, 14:32:05 UTC.DE 7 on the wire
Bitmap position
DE 7 is bit 7 of the primary bitmap: byte 1, mask 0x02. A primary bitmap with only DE 7 present reads 0200000000000000 in hex.
Length
DE 7 is fixed length: always 10 digits, with no length prefix. A parser reads exactly that many and moves on, so shorter values are right-aligned and padded with leading zeros.
Size in the message
At most 10 bytes when the message travels as text (ASCII or EBCDIC), or 5 bytes in binary dialects that pack digits as BCD.
Format n
Format n means numeric: the digits 0–9 only.
Specification reference
Defined in ISO 8583:1987 (base). Card networks publish their own dialect tables (Visa BASE I / V.I.P., Mastercard CIS) that refine formats, lengths, and — for private-use elements — the entire layout. Always confirm against the interface specification you implement.