Literal Constructors

M's #-prefixed literal constructors create typed values inline — #date, #datetime, #datetimezone, #time, #duration, #binary, and #table — without calling conversion functions.

M has a set of built-in literal constructors — keywords prefixed with # — that create typed values directly in source code. Unlike calling a conversion function such as Date.From, literal constructors declare both the type and value in one expression and evaluate to a precise, fully-typed M value.

Available Literal Constructors

#date(year, month, day) — produces a date

#date(2024, 3, 15)

#time(hour, minute, second) — produces a time

#time(14, 30, 0)

#datetime(year, month, day, hour, minute, second) — produces a datetime

#datetime(2024, 3, 15, 14, 30, 0)

#datetimezone(year, month, day, hour, minute, second, offsetHours, offsetMinutes) — produces a datetimezone

#datetimezone(2024, 3, 15, 14, 30, 0, -5, 0)

#duration(days, hours, minutes, seconds) — produces a duration

#duration(1, 2, 30, 0)

#table(columnNames, rows) — produces a table

#table({"Name", "Score"}, {{"Alice", 95}, {"Bob", 82}})

#binary(bytes) — produces a binary

#binary({72, 101, 108, 108, 111})

Why Use Literal Constructors?

Precision and clarity. #date(2024, 3, 15) is unambiguous — it is always March 15, 2024, regardless of locale, system settings, or column type coercion. Date.From("2024-03-15") works but parses a string; the result depends on how the parser interprets the input.

Type safety. The value returned by #datetime(...) is always of type datetime. Conversion functions such as DateTime.From may return null or throw on unexpected input. Literal constructors enforce validity at the syntax level — invalid arguments (e.g. month 13) produce an error immediately.

No dependency on external context. #table lets you embed a complete table inline without connecting to any data source, making it ideal for reference tables, test fixtures, and lookup structures.

Arithmetic with Temporal Literals

The temporal literal constructors integrate naturally with M's arithmetic operators:

// Date arithmetic — produces a date
#date(2024, 1, 1) + #duration(30, 0, 0, 0)
// Result: #date(2024, 1, 31)

// Subtracting two dates — produces a duration
#date(2024, 12, 31) - #date(2024, 1, 1)
// Result: #duration(365, 0, 0, 0)

// Combining date and time — produces a datetime
#date(2024, 3, 15) + #time(14, 30, 0)
// Result: #datetime(2024, 3, 15, 14, 30, 0)

`#table` for Inline Reference Tables

#table is especially useful for embedding small lookup or parameter tables directly in a query, eliminating the need for an external data source:

let
    StatusMap = #table(
        {"Code", "Label"},
        {{1, "Active"}, {2, "Inactive"}, {3, "Pending"}}
    ),
    Result = Table.SelectRows(StatusMap, each [Code] = 2)
in
    Result
// Returns a one-row table: Code = 2, Label = "Inactive"

For columns with enforced types, pass a table type as the first argument instead of a list:

#table(
    type table [Code = number, Label = text],
    {{1, "Active"}, {2, "Inactive"}}
)

Common Pitfalls

Mixing date and datetime. #date(2024, 3, 15) and #datetime(2024, 3, 15, 0, 0, 0) are not equal — M's type system treats them as different types and direct comparison will error.

Duration is not a number. You cannot multiply #duration(1, 0, 0, 0) by a scalar. Use Duration.TotalDays to get a number, perform the multiplication, then use Duration.From to reconstruct.

#datetimezone offset is not converted. The literal #datetimezone(2024, 3, 15, 14, 30, 0, -5, 0) represents 14:30 at UTC-5. If you want UTC, use DateTimeZone.ToUtc rather than manually adjusting the hour argument.