LastUpdateTime (FIX tag 779)

UTCTimestampFIX 4.4

LastUpdateTime (tag 779) is an UTCTimestamp field defined in FIX 4.4. It appears in 2 message types, always optionally.

At a glance

Tag: 779
Name: LastUpdateTime
Datatype: UTCTimestamp (String)
Format: YYYYMMDD-HH:MM:SS[.sss]
Dialects: FIX 4.4
Messages: 2

What the specification says

Timestamp of last update to data item (or creation if no updates made since creation).

Descriptions are quoted from the FIX Orchestra sources under the Apache 2.0 licence.

A real message using tag 779

SettlementInstructionRequest · FIX 4.4

Tag	Field	Wire value	Meaning
8	BeginString	FIX.4.4
9	BodyLength	127
35	MsgType	AV	Settlement Instruction Request
49	SenderCompID	BOARTEAM
56	TargetCompID	COUNTERPARTY
34	MsgSeqNum	2
52	SendingTime	20240101-12:00:00.000
791	SettlInstReqID	EXAMPLE
60	TransactTime	20240101-12:00:00.000
779	LastUpdateTime	20240101-12:00:00.000
10	CheckSum	210

Edit and decode it yourself

Shown with | separators for readability. On the wire FIX uses SOH (0x01), an invisible control byte — and because BodyLength and CheckSum are computed over the actual bytes, the two forms have different checksums. Both are valid and both decode here.

Open in the full decoder →

Generated from the FIX 4.4 dictionary and verified at build time: it parses and validates with no issues. Open the decoder to try your own message.

Where tag 779 appears

Requiredness is a property of the message, not of the field: the same tag can be optional in one message and conditionally required in another.

Message	MsgType	Requiredness	Where in the message
SettlementInstructionRequest	AV	Optional	directly on the message body
SettlementInstructions	T	Conditional	inside the SettlInstGrp component

Wire format

A UTC date and time. The fractional-seconds part is optional, so two timestamps can be equal but not byte-identical. @boarteam/fix keeps the value as a string; format rules are checked by validate(), which reports validate/invalid-value rather than throwing.

Read tag 779 in TypeScript

decode.tsts

import { createFixEngine } from "@boarteam/fix";import { dictionary } from "@boarteam/fix-dict-fix44";const fix = createFixEngine(dictionary);const { message, issues } = fix.parse(raw);const field = message.fields[779];field?.name;   // "LastUpdateTime"field?.raw;    // the verbatim wire stringfield?.value;  // coerced to a string

Decode this in your own code

The same engine that produced the decoded example above is an Apache-2.0 npm package with zero runtime dependencies. It runs in Node and in the browser, and parse() returns problems as data instead of throwing.

npm i @boarteam/fix @boarteam/fix-dict-fix44

Try the decoder Source on GitHub