One API call turns next Monday at 9am into a precise, timezone-aware ISO 8601 datetime. Deterministic. Auditable. No hallucinations.
Temporal reasoning is one of the most consistent failure modes in every major model. Here's why you can't trust it.
Ask an LLM what's next Monday? ten times. The phrasing, the temperature, even the conversation history changes the answer. You can't build reliable software on that.
9am Monday — but in which timezone? Any LLM assumes UTC, or guesses from context. Biruni requires an IANA timezone and handles DST transitions correctly.
Next Friday on a Friday — is that today or next week? Any LLM picks one silently. Biruni flags both options and lets the agent decide.
No SDK. No parsing library. One HTTP call and you're done.
Your agent pulls the temporal expression from the user's message.
POST the phrase with a reference date and timezone. No LLM in the loop.
ISO 8601 with confidence score and audit trail. If ambiguous, Biruni tells you.
Rule-based parser, not probabilistic. Same input, same output, every time. No model drift. No surprises.
Full IANA timezone database. DST transitions handled correctly. UTC offsets always accurate in the response.
When an expression has multiple valid interpretations, Biruni returns all of them. Your agent decides, not a coin flip.
Every response explains how the phrase was interpreted. Perfect for audit logs, agent reasoning chains, and debugging.
High, medium, or low. Your agent knows when to proceed immediately and when to ask the user for clarification.
No neural network in the loop. Pure computation. Fast enough for real-time agent workflows and interactive chat.
Register the tool schema. Paste the usage rules into your system prompt. Your agent calls Biruni instead of doing date math itself.
{
"name": "biruni_resolve",
"description": "Resolve a natural-language temporal phrase to a timezone-aware ISO 8601 datetime.",
"inputSchema": {
"type": "object",
"properties": {
"expression": { "type": "string" },
"reference_date": { "type": "string" },
"timezone": { "type": "string" },
"options": { "type": "object" }
},
"required": ["expression", "reference_date", "timezone"]
}
}
No credit card. Paid tiers with higher limits coming soon.
Coming soon
tomorrow,
in 3 days), weekdays
(next Monday), business days
(in 10 business days with the
default us_federal calendar),
ordinal
patterns (first Monday of
April), absolute dates (March 30, 2026),
and time combinations (next Friday at
3pm). See the full
list in our docs.
status:
"ambiguous" with the most likely interpretation plus an array of alternatives.
Your agent can present the options to the user instead of silently picking the wrong one.
us_federal calendar by default,
which skips weekends plus observed US Federal holidays. The selected calendar is returned in
metadata.calendar_used, and any
skipped holidays appear in metadata.holidays_applied.
America/New_York, Europe/London, Asia/Tokyo, and hundreds more.
Abbreviations like EST or PST are not accepted to avoid ambiguity.
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