Structured Log — Ten Timestamp Formats, One Instant (jsonl)
The same instant written ten ways — RFC 3339 at three precisions and with a non-UTC offset, epoch seconds as integer and float, epoch milliseconds and nanoseconds, Common Log Format and the log4j comma-decimal form. What a timestamp autodetector must resolve to one moment.
{"ts":"2026-03-17T09:14:32.850Z","fmt":"rfc3339_millis","level":"info","msg":"canonical form"}
{"ts":"2026-03-17T09:14:32.850000000Z","fmt":"rfc3339_nanos","level":"info","msg":"nanosecond precision"}
{"ts":"2026-03-17T09:14:32Z","fmt":"rfc3339_seconds","level":"info","msg":"no fractional part"}
{"ts":"2026-03-17T09:14:32.850+02:00","fmt":"rfc3339_offset","level":"info","msg":"non-UTC offset, same instant"}
{"ts":1773738872,"fmt":"epoch_seconds","level":"info","msg":"integer seconds"}
{"ts":1773738872.85,"fmt":"epoch_seconds_float","level":"info","msg":"float seconds"}
{"ts":1773738872850,"fmt":"epoch_millis","level":"info","msg":"integer milliseconds"}
{"ts":1773738872850000000,"fmt":"epoch_nanos","level":"info","msg":"integer nanoseconds, beyond 2^53"}
{"ts":"17/Mar/2026:09:14:32 +0000","fmt":"clf","level":"info","msg":"common log format stamp"}
{"ts":"2026-03-17 09:14:32,850","fmt":"log4j","level":"info","msg":"comma as the decimal separator"}
Specifications
- Lines
- 10
- Distinct Formats
- 10
- Same Instant
- true
- Instant Utc
- 2026-03-17T09:14:32.850Z
- Includes Non Utc Offset
- true
- Epoch Nanos Exceeds Float53
- true
Testing contract
Expected to pass- Scenario
- Auto-detect each ts field and normalise it to UTC.
- Expected result
- All ten records resolve to 2026-03-17T09:14:32.850Z (the seconds-precision record to the same second), including the +02:00 offset record and the nanosecond integer that overflows a double.
What is a .jsonl file?
JSONL (JSON Lines) is a text format where each line is a complete, independent JSON value, allowing records to be streamed and appended without parsing the whole file. It is not itself a JSON array and each line must stand alone. It is common in logging, machine learning datasets, and data pipelines.
How to use this file
Use an example JSONL to test line-by-line streaming parsers, append-and-resume ingestion, and batch pipelines that process one record per line.
How to use this file for testing
“Structured Log — Ten Timestamp Formats, One Instant (jsonl)” is a deterministic Novus Examples fixture for Observability, Log parsing, Encoding detection. Structured and plain-text telemetry with known timestamps, levels, request identifiers, and error states for testing log ingestion, correlation, dashboards, and alert pipelines.
Documented properties for this file: JSONL · 961 bytes. Compare results against paired or grouped companions on this page when present (clean↔damaged, searchable↔scanned, or format twins) so scores stay reproducible across runs.
Download the file once, keep the path stable in CI or local scripts, and treat the spec table as the contract: dimensions, seeds, field lists, and roles are intentional. Corrupt or invalid samples are labelled as such — expect parsers to fail loudly rather than silently accept them.
Telemetry fixtures use fixed trace IDs, span IDs, and timestamps so ingestion is reproducible run to run. Point your collector, parser, or query layer at the file and assert the documented span tree, metric families, or severity mix; service and host names are invented.
Code examples
import json
with open("app-mixed-timestamp-formats.jsonl") as f:
rows = [json.loads(line) for line in f]
print(len(rows), rows[0])Related files
- loglogfmt — Quoting, Escaping and Bare-Key Edge Cases (log)logfmt lines built to break naive splitting on spaces and equals signs: a value containing an equals sign, escaped quotes, a trailing backslash before the closing quote, a bare key with no value, duplicate keys, non-ASCII values and one unterminated quote followed by a clean line.
- logPlain-Text Log — ANSI Colour Codes in the Stream (log)A developer-mode log where the level and service are wrapped in ANSI colour codes, ending with one uncoloured line. Colour codes sit inside the field a parser wants to read, so level extraction fails unless the sequences are stripped first — the classic symptom of a container run without a TTY check.
- logPlain-Text Log — Mixed CRLF and LF Line Endings (log)One log file written by two agents, four lines ending CRLF and three LF, with one line carrying trailing spaces before its break. Splitting on \n alone leaves a stray carriage return at the end of four fields, which is how a level or status ends up with an invisible character attached.
- logPlain-Text Log — NUL, Control Bytes and Invalid UTF-8 (log)Five log lines carrying a NUL byte, bell, backspace, vertical tab and form feed, plus one 0xFF byte that is not valid UTF-8 — the debris that arrives when binary data reaches a log field. Deliberately contains no terminal-escape sequences, only inert control bytes.
- jsonlStructured Log — Unicode, RTL, Emoji and Control Characters (jsonl)Log messages in Latin, Japanese and Arabic scripts, an emoji flag and a zero-width-joiner family, NFC and NFD forms of the same accented letter, and escaped tab, newline and carriage return. Everything that makes a log line's byte length and its display width disagree.
- txtProfile — Demangled Symbols That Break the Folded Format (txt)Demangled C++ templates, Rust trait impls, Java generics, lambdas and unresolved hex addresses in the folded format — including one symbol containing a semicolon, which the format has no way to escape. That line is genuinely ambiguous, and how a parser handles it is the point.
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