dateparser is a smart and high-performance datetime parser library, it supports hundreds of different patterns.
For better performance and flexibility,
dateparser doesn't use SimpleDateFormat or DateTimeFormatter,
but uses retree to parse the specified String into several matched parts,
and convert different parts to be different properties like year, month, day, hour, minute, second, zone etc.
dateparser has lots of predefined regular expressions as rules, like:
(?<week>%s)\W* to match Monday as week?(?<year>\d{4})$ to match 2019 as year^(?<year>\d{4})(?<month>\d{2})$ to match 201909 as year and month?(?<hour>\d{1,2}) o’clock\W* to match 12 o’clock as hourDateParserBuilder.javaWith so many regular expressions, if use java.util.regex.Pattern to match them one by one,
the performance would be a disaster.
So I choice to use retree, retree could merge lots of regular expressions as one,
in my opinion, it is more like a tree, which could execute matching quickly and concurrently.
You can also customize your own parser, by add new rules.
Add maven dependency:
<dependency>
<groupId>com.github.sisyphsu</groupId>
<artifactId>dateparser</artifactId>
<version>1.0.4</version>
</dependency>Parse String into Date, Calendar, LocalDateTime, OffsetDateTime:
Date date = DateParserUtils.parseDate("Mon Jan 02 15:04:05 -0700 2006");
// Tue Jan 03 06:04:05 CST 2006
Calendar calendar = DateParserUtils.parseCalendar("Fri Jul 03 2015 18:04:07 GMT+0100 (GMT Daylight Time)");
// 2015-07-03T17:04:07Z
LocalDateTime dateTime = DateParserUtils.parseDateTime("2019-09-20 10:20:30.12345678 +0200");
// 2019-09-20T16:20:30.123456780
OffsetDateTime offsetDateTime = DateParserUtils.parseOffsetDateTime("2015-09-30 18:48:56.35272715 +0000 UTC");
// 2015-09-30T18:48:56.352727150ZPlease notice the TimeZone and ZoneOffset like -0700, it could affect time.
Because DateParser isn't thread safe, and the parse operation is quite fast(about 1us),
so DateParserUtils maintains one parser as default, and wrap it with synchronized.
If you want to use it concurrently, you should create new parser like this:
DateParser parser = DateParser.newBuilder().build();
Date date = parser.parseDate("Mon Jan 02 15:04:05 -0700 2006");
// Tue Jan 03 06:04:05 CST 2006The DateParser's instance is a little heavy, you should try to reuse it.
MM/dd or dd/MMFor most cases, dateparser could recognize which part is month and which part is day.
But for MM/dd/yy and dd/MM/yy, it would be confused,
because most of countries use dd/MM/yy, but little of countries use MM/dd/yy, which is mainly the USA.
So dateparser will use dd/MM as priority, but you could change it by:
DateParserUtils.preferMonthFirst(true);
DateParserUtils.parseCalendar("08.03.71");
// 1971-08-03
DateParserUtils.preferMonthFirst(false);
DateParserUtils.parseCalendar("08.03.71");
// 1971-03-08Notice: if either number is larger than 12, then preferMonthFirst wouldn't be effective.
You could use DateParserBuilder to build your own parser,
and customize new rules to parse different input.
Like add support for 【2019】, which isn't supported by default:
DateParser parser = DateParser.newBuilder().addRule("【(?<year>\\d{4})】").build();
Calendar calendar = parser.parseCalendar("【1991】");
assert calendar.get(Calendar.YEAR) == 1991;The group name year is very important, you cannot use other unknown name.
But, you can register new handler to parse the new rule:
DateParser parser = DateParser.newBuilder()
.addRule("民国(\\d{3})年", (input, matcher, dt) -> {
int offset = matcher.start(1);
int i0 = input.charAt(offset) - '0';
int i1 = input.charAt(offset + 1) - '0';
int i2 = input.charAt(offset + 2) - '0';
dt.setYear(i0 * 100 + i1 * 10 + i2 + 1911);
})
.build();
Calendar calendar = parser.parseCalendar("民国101年");
assert calendar.get(Calendar.YEAR) == 2012;The 民国101年 represents 101 years after 1911.
Compared to single SimpleDateFormat, the performance of dateparser:
Benchmark Mode Cnt Score Error Units
SingleBenchmark.java avgt 6 921.632 ± 12.299 ns/op
SingleBenchmark.parser avgt 6 1553.909 ± 70.664 ns/opCompared to single DateTimeFormatter, the performance of dateparser:
Benchmark Mode Cnt Score Error Units
SingleDateTimeBenchmark.java avgt 6 654.553 ± 16.703 ns/op
SingleDateTimeBenchmark.parser avgt 6 1680.690 ± 34.214 ns/opSo, for String with known format, the dateparser is slower.
But if the number of format is not single,
lets increase to 16, the performance of dateparser:
Benchmark Mode Cnt Score Error Units
MultiBenchmark.format avgt 6 47385.021 ± 1083.649 ns/op
MultiBenchmark.parser avgt 6 22852.113 ± 310.720 ns/opdateparser is very stable, with increasing of the number of format, it has no performance lose.
You can checkout the source code of benchmark at there.
There are some examples of datetime format which dateparser supports:
May 8, 2009 5:57:51 PM
oct 7, 1970
oct 7, '70
oct. 7, 1970
oct. 7, 70
Mon Jan 2 15:04:05 2006
Mon Jan 2 15:04:05 MST 2006
Mon Jan 02 15:04:05 -0700 2006
Monday, 02-Jan-06 15:04:05 MST
Mon, 02 Jan 2006 15:04:05 MST
Tue, 11 Jul 2017 16:28:13 +0200 (CEST)
Mon, 02 Jan 2006 15:04:05 -0700
Thu, 4 Jan 2018 17:53:36 +0000
Mon Aug 10 15:44:11 UTC+0100 2015
Fri Jul 03 2015 18:04:07 GMT+0100 (GMT Daylight Time)
September 17, 2012 10:09am
September 17, 2012 at 10:09am PST-08
September 17, 2012, 10:10:09
October 7, 1970
October 7th, 1970
12 Feb 2006, 19:17
12 Feb 2006 19:17
7 oct 70
7 oct 1970
03 February 2013
1 July 2013
2013-Feb-03
3/31/2014
03/31/2014
08/21/71
8/1/71
4/8/2014 22:05
04/08/2014 22:05
4/8/14 22:05
04/2/2014 03:00:51
8/8/1965 12:00:00 AM
8/8/1965 01:00:01 PM
8/8/1965 01:00 PM
8/8/1965 1:00 PM
8/8/1965 12:00 AM
4/02/2014 03:00:51
03/19/2012 10:11:59
03/19/2012 10:11:59.3186369
2014/3/31
2014/03/31
2014/4/8 22:05
2014/04/08 22:05
2014/04/2 03:00:51
2014/4/02 03:00:51
2012/03/19 10:11:59
2012/03/19 10:11:59.3186369
2014年04月08日
2006-01-02T15:04:05+0000
2009-08-12T22:15:09-07:00
2009-08-12T22:15:09
2009-08-12T22:15:09Z
2014-04-26 17:24:37.3186369
2012-08-03 18:31:59.257000000
2014-04-26 17:24:37.123
2013-04-01 22:43
2013-04-01 22:43:22
2014-12-16 06:20:00 UTC
2014-12-16 06:20:00 GMT
2014-04-26 05:24:37 PM
2014-04-26 13:13:43 +0800
2014-04-26 13:13:43 +0800 +08
2014-04-26 13:13:44 +09:00
2012-08-03 18:31:59.257000000 +0000 UTC
2015-09-30 18:48:56.35272715 +0000 UTC
2015-02-18 00:12:00 +0000 GMT
2015-02-18 00:12:00 +0000 UTC
2015-02-08 03:02:00 +0300 MSK m=+0.000000001
2015-02-08 03:02:00.001 +0300 MSK m=+0.000000001
2017-07-19 03:21:51+00:00
2014-04-26
2014-04
2014
2014-05-11 08:20:13,787
3.31.2014
03.31.2014
08.21.71
2014.03
2014.03.30
20140601
20140722105203
1332151919
1384216367189
1384216367111222
1384216367111222333 Lots of these examples were copied from https://github.com/araddon/dateparse.
Let me know if you meet any issues when using this library.
Let me know if you need any features that this library hasn't yet.
Pull Request are welcomed.
MIT