A minimalist DateTime library for validating, parsing, manipulating and formatting times.


This will add a like this to you packages pubspec.yaml file:

  now: latest

Or you can install it from the command line:

dart pub add now


Now is an MIT licensed open source project with its ongoing development made possible entirely by the support of these awesome backers. If you'd like to join them, please consider sponsoring Odroe development.


Getting Started

Create a DateTime

/// Create a new DateTime from local time zone.
final current = now(); // Same as
final utc = now.utc(); // Same as

Format a DateTime

final pattern = 'YYYY-MM-DD HH:mm:ss.SSS';
final formated = now().format(pattern); // Same as

print(formated); // 2021-08-01 12:00:00.000

Convert a DateTime

Obtained a UTC safely originally from a different time zone.

final utc = date.isUtc ? date : date.toUtc();

Now you can convert it to a UTC time zone.

final utc = date.utc; // Same as date.isUtc ? date : date.toUtc();

DateTime addition and subtraction

final date = now();

/// Add 1 day.
final tomorrow = date +; // Same as date.add(Duration(days: 1));

/// Subtract 1 day.
final yesterday = date -; // Same as date.subtract(Duration(days: 1));

DateTime comparison

  • Compare DateTime with DateTime less than or equal.

    final date1 = now();
    final date2 = date1 +;
    print(date1 <= date2); // true
    print(date1.isBeforeOrEqual(date2)); // true
  • Compare DateTime with DateTime greater than or equal.

    final date1 = now();
    final date2 = date1 +;
    print(date2 >= date1); // true
    print(date2.isAfterOrEqual(date1)); // true
  • Compare DateTime with DateTime less than.

    final date1 = now();
    final date2 = date1 +;
    print(date1 < date2); // true
    print(date1.isBefore(date2)); // true
  • Compare DateTime with DateTime greater than.

    final date1 = now();
    final date2 = date1 +;
    print(date2 > date1); // true
    print(date2.isAfter(date1)); // true

Duration extensions

Weeks in the duration

final Duration duration = Duration(days: 7);

print(duration.inWeeks); // 1

Convert a int to a Duration

Unit Same as Description Example
microseconds Duration(microseconds: <int>) Microseconds in the duration 1.microsecond
milliseconds Duration(milliseconds: <int>) Milliseconds in the duration 1.millisecond
seconds Duration(seconds: <int>) Seconds in the duration 1.second
minutes Duration(minutes: <int>) Minutes in the duration 1.minute
hours Duration(hours: <int>) Hours in the duration 1.hour
days Duration(days: <int>) Days in the duration
weeks Duration(days: <int> * 7) Weeks in the duration 1.week

Format specifiers

By default we register all the built-in formatters.

specifier Description Example
A AM/PM Upper case now().format('A') -> AM
a am/pm Lower case now().format('a') -> am
D Day of month, 1-31 now().format('D') -> 1
DD Day of month, 01-31 now().format('DD') -> 01
d Day of week, 1-7 now().format('d') -> 1
dd Day of week min name now().format('dd') -> Mo
ddd Day of week short name now().format('ddd') -> Mon
dddd Day of week full name now().format('dddd') -> Monday
H Hour, 0-23 now().format('H') -> 0
HH Hour, 00-23 now().format('HH') -> 00
h Hour, 1-12 now().format('h') -> 1
hh Hour, 01-12 now().format('hh') -> 01
SSS Milliseconds, 000-999 now().format('SSS') -> 000
m Minute, 0-59 now().format('m') -> 0
mm Minute, 00-59 now().format('mm') -> 00
M Month, 1-12 now().format('M') -> 1
MM Month, 01-12 now().format('MM') -> 01
MMM Month abbreviated name now().format('MMM') -> Jan
MMMM Month full name now().format('MMMM') -> January
Q Quarter, 1-4 now().format('Q') -> 1
s Second, 0-59 now().format('s') -> 0
ss Second, 00-59 now().format('ss') -> 00
YY Year, 00-99 now().format('YY') -> 21
YYYY Year, 0000-9999 now().format('YYYY') -> 2023
Z Timezone now().format('Z') -> +01:00
ZZ Timezone now().format('ZZ') -> +0100

Escape specifiers

Occasionally, single-character specifiers exist for formatters. Our formatting mode hopes that this string will not be processed by the formatter, but will output the characters we defined as it is.

  • \ Prefix, a character after the \ symbol ensures output as is.

    now().format('HH:mm A ss'); // 00:00 AM 00
    // This is not what we expect, since the second s needs to be output as-is.
    now().format(r'HH:mm A s\s'); // 00:00 AM 0s
    // Or
    now().format('HH:mm A s\\s'); // 00:00 AM 0s

DateTime formatter

Sometimes the built-in formatter cannot meet all your needs, you can register a DateTime formatter via now.register:

final DateTimeFormatter formatter = ...


You may already have a DateTime formatter, but its specifier is not what you expect:

final DateTimeFormatter formatter = ...

now.registerWith('Custom specifier', formatter);

Custom formatter

If you wish to customize the DateTime formatter, you need to implement the DateTimeFormatter interface imported from package:now/formatter.dart:

import 'package:now/formatter.dart';

class MyFormatter implements DateTimeFormatter {
  const MyFormatter();

  /// Matched the [specifier] and return the [DateTime] format result.
  String format(DateTime dateTime) {
    // TODO: format the [dateTime] and return the result.
    return 'My format result';

  String get specifier => 'My specifier';

Then we register and use it:

import 'package:now/now.dart';

main() {
  now.register(const MyFormatter());

  print(now().format('YYYY - My specifier')); // Output: 2023 - My format result

Function-based formatter

If you don't want to implement the DateTimeFormatter interface, you can also use the function-based formatter:

import 'package:now/now.dart';

main() {
  now.registerWithFn('My specifier', (dateTime) {
    return 'My format result';

  print(now().format('YYYY - My specifier')); // Output: 2023 - My format result


We provide a helper method for Stopwatch that can be directly created and started:

final stopwatch = now.stopwatch(); // Same as Stopwatch()..start()

Destroy formatters

Method Description Example
now.destroy() Destroys a registered with a test function. now.destroy((f) => f.specifier == 'A')
now.destroyAll() Destroys all registered formatters. now.destroyAll()
now.destroyWith() Destroys a registered formatter. now.destroyWith('A')
now.destroyDefault() Destroys all built-in formatters. now.destroyDefault()


We welcome contributions! Please read our contributing guide to learn about our development process, how to propose bugfixes and improvements, and how to build and test your changes to Prisma.

Thank you to all the people who already contributed to Odroe!


Code of Conduct

This project has adopted the Contributor Covenant Code of Conduct. For more information see the Code of Conduct FAQ or contact with any additional questions or comments.

Stay in touch


A minimalist DateTime extension for validating, parsing, manipulating and formatting times.
DateTime formatter.