Validation

GMT’s public functions never throw on invalid input — they return a sentinel. But when you need to reject invalid input at a system boundary (a form, an API parameter, a config file), use these validators to check first.

Scalar validation

import { isValidDate, isValidTime, isValidDateTime } from "@northguild/gmt";

isValidDate("2024-03-15"); // true
isValidDate("2024-02-30"); // false — invalid day
isValidTime("14:30:45"); // true
isValidTime("25:00:00"); // false — invalid hour
isValidDateTime("2024-03-15T14:30:45"); // true

Timezone and zoned-datetime validation

import { isValidTimeZone, isValidZonedDateTime } from "@northguild/gmt/zoned";

isValidTimeZone("America/New_York"); // true
isValidTimeZone("Invalid/Zone"); // false

isValidZonedDateTime("2024-03-15T14:30:45[America/New_York]"); // true
isValidZonedDateTime("2024-02-30T14:30:45[America/New_York]"); // false

Daylight saving time

import { hasDaylightSaving, getDstTransitions } from "@northguild/gmt/zoned";

hasDaylightSaving("America/New_York"); // true
hasDaylightSaving("Asia/Tokyo"); // false

getDstTransitions("America/New_York", 2024);
// [
//   { instant: "2024-03-10T07:00:00Z", offsetBefore: "-05:00", offsetAfter: "-04:00" },
//   { instant: "2024-11-03T06:00:00Z", offsetBefore: "-04:00", offsetAfter: "-05:00" }
// ]

getDstTransitions("Asia/Tokyo", 2024); // [] — no transitions

Duration-unit validation

import { isValidDateUnit, isValidTimeUnit } from "@northguild/gmt";

isValidDateUnit("day"); // true
isValidTimeUnit("hour"); // true
isValidDateUnit("invalid"); // false

Interval validation (positional args, start ≤ end)

import {
  isValidDateInterval,
  isValidTimeInterval,
  isValidDateTimeInterval,
} from "@northguild/gmt";

isValidDateInterval("2024-01-01", "2024-12-31"); // true
isValidDateInterval("2024-12-31", "2024-01-01"); // false — start > end
isValidTimeInterval("09:00:00", "17:00:00"); // true
isValidDateTimeInterval("2024-01-01T10:00:00", "2024-12-31T23:59:59"); // true

There are isValidUtcInterval, isValidUnixInterval, and isValidZonedInterval siblings. All return false on invalid input.

Range validation (object params)

Range validators take { value1, value2, options? } — a different shape from the interval validators above:

import { isValidDateRange, isValidZonedRange } from "@northguild/gmt";

isValidDateRange({ value1: "2024-01-01", value2: "2024-12-31" }); // true
isValidZonedRange({
  value1: "2024-01-01T10:00:00+00:00[UTC]",
  value2: "2024-12-31T23:59:59+00:00[UTC]",
}); // true

Don’t confuse the two: isValidDateInterval takes positional (start, end) args; isValidDateRange takes an object { value1, value2 }.

See also

• Parsing — extracting components from validated strings
• Intervals — containment, overlap, and set operations on validated ranges
• isValidDate reference
• isValidTimeZone reference
• hasDaylightSaving reference