Moment applies stricter initialization rules than the constructor.

    You can check whether the Moment considers the date invalid using moment#isValid. You can check the metrics used by #isValid using moment#parsingFlags, which returns an object.

    The following parsing flags result in an invalid date:

    • overflow: An overflow of a date field, such as a 13th month, a 32nd day of the month (or a 29th of February on non-leap years), a 367th day of the year, etc. overflow contains the index of the invalid unit to match #invalidAt (see below); -1 means no overflow.
    • invalidMonth: An invalid month name, such as moment('Marbruary', 'MMMM');. Contains the invalid month string itself, or else null.
    • empty: An input string that contains nothing parsable, such as moment('this is nonsense');. Boolean.
    • nullInput: A null input, like moment(null);. Boolean.
    • invalidFormat: An empty list of formats, such as moment('2013-05-25', []). Boolean.

    • userInvalidated: A date created explicitly as invalid, such as moment.invalid(). Boolean.
      In addition to the above, As of 2.13.0 the meridiem and parsedDateParts flags work together to determine date validity.

    • meridiem: Indicates what meridiem (AM/PM) was parsed, if any. String.

    • unusedTokens: array of format substrings not found in the input string

    • unusedInput: array of input substrings not matched to the format string
      Note: Moment's concept of validity became more strict and consistent between 2.2 and 2.3.Note: Validity is determined on moment creation. A modified moment (i.e. moment().hour(NaN)) will remain valid.

    Additionally, you can use moment#invalidAt to determine which date unit overflowed.

    The return value has the following meaning:

    • years
    • months
    • days
    • hours
    • minutes
    • seconds
    • milliseconds
      Note: In case of multiple wrong units the first one is returned (becausedays validity may depend on month, for example).

    Invalid Moments

    If a moment is invalid, it behaves like a NaN in floating point operations.

    All of the following produce invalid moments:

    • another.add(invalid)
    • invalid.diff(another)
    • invalid.endOf(unit)
    • invalid.max(another)
    • another.max(invalid)
    • invalid.min(another)
    • another.min(invalid)
    • invalid.set(unit, value)
    • invalid.startOf(unit)

    • invalid.format(anyFmt) results in 'Invalid Date' in the current locale

    • invalid.from(another)
    • another.from(invalid)
    • invalid.fromNow(suffix)
    • invalid.to(another)
    • another.to(invalid)
    • invalid.toNow(suffix)
    • invalid.toISOString() (Before 2.18.0)

    • invalid.toString()
      The following return false:

    • invalid.isAfter(another)

    • invalid.isBefore(another)
    • invalid.isBefore(invalid)
    • another.isBefore(invalid)
    • invalid.isBetween(another, another)
    • invalid.isBetween(invalid, invalid)
    • invalid.isSame(another)
    • invalid.isSame(invalid)
    • another.isSame(invalid)
    • invalid.isSameOrAfter(another)
    • invalid.isSameOrAfter(invalid)
    • another.isSameOrAfter(invalid)
    • invalid.isSameOrBefore(another)
    • invalid.isSameOrBefore(invalid)

    • another.isSameOrBefore(invalid)
      And these return null or NaN with some structure:

    • invalid.get(unit) returns null, as all other named getters

    • invalid.toArray() === [NaN, NaN, NaN, NaN, NaN, NaN]
    • invalid.toObject() has all values set to NaN
    • invalid.toDate() returns an invalid Date object
    • invalid.toJSON() returns null
    • invalid.unix() returns null
    • invalid.toISOString() returns null (As of 2.18.0)