moment to Temporal

This codemod migrates common moment and moment-timezone usage to Temporal equivalents. It rewrites frequently used patterns such as “now”, add/subtract chains, simple formatting, parsing, durations, timezone conversion, and validation checks.

It also supports migrating a limited Luxon entrypoint (DateTime.local()) to Temporal in mixed codebases.

Goal

• Replace common moment APIs with Temporal equivalents.
• Remove moment / moment-timezone / luxon imports when transformed.
• Keep transformed code explicit and readable.
• Cover common migration paths while surfacing edge cases for review.

Example

Replace moment() + .format()

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- import moment from 'moment';
- const now = moment();
- console.log(now.format());
+ const now = Temporal.Now.zonedDateTimeISO();
+ console.log(now.toString());

Replace add/subtract chaining

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- import moment from 'moment';
- const m = moment().add(3, 'days').subtract(4, 'hours');
- console.log(m.format());
+ let z = Temporal.Now.zonedDateTimeISO();
+ z = z.plus({ days: 3 });
+ z = z.minus({ hours: 4 });
+ console.log(z.toString());

Replace simple date formatting (YYYY-MM-DD)

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- import moment from 'moment';
- const s = moment().format('YYYY-MM-DD');
+ const s = Temporal.Now.plainDateISO().toString();

Replace moment.tz(...)

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- import moment from 'moment-timezone';
- const m = moment.tz('2020-03-08 02:30', 'America/Los_Angeles');
- console.log(m.format());
+ const dt = Temporal.PlainDateTime.from('2020-03-08T02:30:00');
+ const tz = Temporal.TimeZone.from('America/Los_Angeles');
+ const instants = tz.getPossibleInstantsFor(dt);
+ const zdt = instants[0].toZonedDateTimeISO(tz.id);
+ console.log(zdt.toString());

Replace locale token formatting (LL)

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- import moment from 'moment';
- moment.locale('fr');
- const s = moment().format('LL');
+ const dt = Temporal.Now.plainDateTimeISO();
+ const s = new Intl.DateTimeFormat('fr', { dateStyle: 'long' }).format(dt);

Replace moment.duration(...)

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- import moment from 'moment';
- const d = moment.duration({ days: 1, hours: 2 });
- const later = moment().add(d);
- console.log(later.format());
+ const d = Temporal.Duration.from({ days: 1, hours: 2 });
+ const later = Temporal.Now.zonedDateTimeISO().plus(d);
+ console.log(later.toString());

What this codemod currently covers

• moment() creation and .format() default usage.
• .add(...) / .subtract(...) chains with common units.
• format('YYYY-MM-DD') to Temporal.Now.plainDateISO().toString().
• Parsing patterns:
  • moment('12/31/2020', 'MM/DD/YYYY')
  • moment('2020-01-02', 'YYYY-MM-DD')
• Timezone pattern: moment.tz(datetime, timezone).
• Unix epoch pattern: moment.unix(seconds).
• Relative time pattern: .fromNow() (rewritten with Intl.RelativeTimeFormat).
• Differences pattern: .diff(..., unit) for covered units.
• Validation patterns:
  • moment('bad').isValid()
  • strict parse shape moment(value, 'YYYY-MM-DD', true).isValid()
• Edge helpers for ordinals, quarters, weeks, start/end of day, UTC/local combinations.
• moment.duration({...}) and add-duration flows.
• Limited Luxon migration: DateTime.local() and .toISO().

Usage

Enable optional Temporal polyfill import insertion via workflow param:

• Param: importPolyfill=true
• Env (supported aliases): IMPORT_POLYFILL=true, CODEMOD_IMPORT_POLYFILL=true, or POLYFILL=true

When enabled, the transform attempts to inject:

• ESM: import { Temporal } from '@js-temporal/polyfill';
• CJS: const { Temporal } = require('@js-temporal/polyfill');

Caveats

• This codemod focuses on known patterns from fixtures and may skip unsupported call shapes.
• Token-rich moment.format(...) cases beyond covered patterns need manual migration.
• Temporal timezone ambiguity resolution (e.g. DST folds/skips) may require project-specific policy.
• Relative time wording can differ from Moment output because it uses Intl.RelativeTimeFormat.
• Always review transformed code and run your app/tests after migration.
• This codemod does not attempt to remove dep of your package.json or handle runtime polyfill loading. You must manage those separately after migration.