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Epoch Calculator

by com.epochcalc

convert_timezone

Read-onlyIdempotent

Convert a wall-clock date/time from one IANA time zone to another, correctly across daylight-saving transitions. Returns both sides with offsets, the hour difference at that instant, and whether either zone is on DST.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
datetimeYesISO 8601 date/time, e.g. "2026-09-06T09:30". If it has no offset it is read as wall time in from_timezone.
to_timezoneYesTarget IANA zone, e.g. "Europe/London".
from_timezoneYesSource IANA zone, e.g. "Asia/Tokyo".

Output Schema

TableJSON Schema
NameRequiredDescriptionDefault
sourceYesOne instant described in one IANA time zone.
targetYesOne instant described in one IANA time zone.
difference_hoursYestarget offset minus source offset, in hours.
same_instant_utcYesThe shared instant as ISO 8601 UTC.

Schema Changelog

Changes observed during successful MCP inspections. Dates show when Glama detected each change.

  1. Changed1 schema field changed
    • changedOutput schema / (root)
      Previous value: -nullNew value: +{
+  "properties": {
+    "difference_hours": {
+      "description": "target offset minus source offset, in hours.",
+      "type": "number"
+    },
+    "same_instant_utc": {
+      "description": "The shared instant as ISO 8601 UTC.",
+      "type": "string"
+    },
+    "source": {
+      "description": "One instant described in one IANA time zone.",
+      "properties": {
+        "abbreviation": {
+          "description": "Zone abbreviation at that instant, e.g. \"BST\".",
+          "type": "string"
+        },
+        "epoch_millis": {
+          "description": "Unix time in milliseconds.",
+          "type": "integer"
+        },
+        "epoch_seconds": {
+          "description": "Unix time in seconds.",
+          "type": "integer"
+        },
+        "human": {
+          "description": "Readable sentence with weekday, date, time and zone.",
+          "type": "string"
+        },
+        "is_dst": {
+          "description": "Whether daylight-saving time is in effect.",
+          "type": "boolean"
+        },
+        "iso": {
+          "description": "ISO 8601 with the zone offset.",
+          "type": "string"
+        },
+        "offset": {
+          "description": "UTC offset, e.g. \"+09:00\".",
+          "type": "string"
+        },
+        "offset_minutes": {
+          "description": "UTC offset in minutes.",
+          "type": "integer"
+        },
+        "rfc2822": {
+          "description": "RFC 2822 date string.",
+          "type": "string"
+        },
+        "timezone": {
+          "description": "IANA zone name.",
+          "type": "string"
+        },
+        "utc_iso": {
+          "description": "ISO 8601 in UTC (Z).",
+          "type": "string"
+        },
+        "weekday": {
+          "description": "Full weekday name in English.",
+          "type": "string"
+        }
+      },
+      "required": [
+        "epoch_seconds",
+        "epoch_millis",
+        "iso",
+        "utc_iso",
+        "timezone",
+        "offset",
+        "offset_minutes",
+        "abbreviation",
+        "is_dst",
+        "weekday",
+        "rfc2822",
+        "human"
+      ],
+      "type": "object"
+    },
+    "target": {
+      "description": "One instant described in one IANA time zone.",
+      "properties": {
+        "abbreviation": {
+          "description": "Zone abbreviation at that instant, e.g. \"BST\".",
+          "type": "string"
+        },
+        "epoch_millis": {
+          "description": "Unix time in milliseconds.",
+          "type": "integer"
+        },
+        "epoch_seconds": {
+          "description": "Unix time in seconds.",
+          "type": "integer"
+        },
+        "human": {
+          "description": "Readable sentence with weekday, date, time and zone.",
+          "type": "string"
+        },
+        "is_dst": {
+          "description": "Whether daylight-saving time is in effect.",
+          "type": "boolean"
+        },
+        "iso": {
+          "description": "ISO 8601 with the zone offset.",
+          "type": "string"
+        },
+        "offset": {
+          "description": "UTC offset, e.g. \"+09:00\".",
+          "type": "string"
+        },
+        "offset_minutes": {
+          "description": "UTC offset in minutes.",
+          "type": "integer"
+        },
+        "rfc2822": {
+          "description": "RFC 2822 date string.",
+          "type": "string"
+        },
+        "timezone": {
+          "description": "IANA zone name.",
+          "type": "string"
+        },
+        "utc_iso": {
+          "description": "ISO 8601 in UTC (Z).",
+          "type": "string"
+        },
+        "weekday": {
+          "description": "Full weekday name in English.",
+          "type": "string"
+        }
+      },
+      "required": [
+        "epoch_seconds",
+        "epoch_millis",
+        "iso",
+        "utc_iso",
+        "timezone",
+        "offset",
+        "offset_minutes",
+        "abbreviation",
+        "is_dst",
+        "weekday",
+        "rfc2822",
+        "human"
+      ],
+      "type": "object"
+    }
+  },
+  "required": [
+    "source",
+    "target",
+    "difference_hours",
+    "same_instant_utc"
+  ],
+  "type": "object"
+}
  2. First observed

TDQS

A4/5.0
Behavior4/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, lowering the burden. The description adds meaningful behavioral context by noting DST-safe conversion and listing the return details (offsets, hour difference, DST status), which goes beyond the annotations.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Two sentences, no filler, and the core purpose is front-loaded. The second sentence concisely summarizes the return value, earning its place without bloating the description.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

The description plus a complete input schema and output schema cover the core usage well. It handles the main DST concern and expected return values, though it could optionally mention edge cases like ambiguous or nonexistent local times; this is not a significant gap.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so the schema already documents all three parameters. The description reinforces the IANA and wall-clock concepts, but it does not add substantial meaning beyond what the schema's parameter descriptions already provide.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific action ('Convert'), a clear resource (wall-clock date/time), and the IANA time zone context. It differentiates itself from siblings like convert_timestamp by emphasizing wall-clock time and DST correctness.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description implies when to use this tool—converting wall-clock times between time zones—and clarifies the DST handling, but it does not explicitly name alternatives or state when not to use it. Usage context is clear, but no exclusions or sibling differentiation guidance is provided.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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TDQS

A4.1/5.0
Disambiguation5/5

Each tool targets a distinct date/time operation: conversion, timezone shifting, cron scheduling, duration, countdown, arithmetic, parsing, and current time. Even the inverse operations (convert_timestamp vs parse_datetime) are clearly separated by input/output direction.

Naming Consistency3/5

Names are uniformly snake_case and readable, but they mix verb_noun patterns (convert_timestamp, parse_datetime) with noun-phrase or query-style names (date_duration, time_now, days_until, epoch_math, cron_next_runs). This is consistent in style but not in grammatical pattern.

Tool Count5/5

Eight tools is well-scoped for a date/time and epoch calculator. Each tool covers a distinct facet of the domain without redundancy or bloat.

Completeness5/5

The tool surface covers the full lifecycle of date/time operations: current time, parsing, formatting, timezone conversion, arithmetic, duration, countdowns, and cron scheduling. No significant gaps that would block common use cases.

Resources