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Date's constructor doesn't behave the same on trimmed and untrimmed strings [duplicate]

Why does Date.parse give incorrect results?Trim string in JavaScript?JavaScript chop/slice/trim off last character in stringHow to trim a file extension from a String in JavaScript?Inconsistant date parsing with missing timezoneCorrectly format times between client (javascript) and the server (PHP)Javascript date string passed to Date constructor gives strange resultsMongoose/MongoDB regex find query using variableGoogle Maps Time Zone API get local time in UTCCreate moment.js date from milliseconds in local timezoneIs there a workaround in JSON Parse and Stringify for Dates when a custom engine doesn't accept the norm

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0

This question already has an answer here:

• 
  Why does Date.parse give incorrect results?
  
  11 answers
  
  

I know that creating a date from string is usually a bad idea, but still, this caught my attention: adding a space before or after the date string can affect the created date value.

console.log([

 new Date('2019-03'), // 2019-03-01T00:00:00.000Z
 new Date('2019-03 '), // 2019-02-28T23:00:00.000Z
 new Date(' 2019-03'), // 2019-02-28T23:00:00.000Z

 new Date('2019-03-05'), // 2019-03-05T00:00:00.000Z
 new Date('2019-03-05 '), // 2019-03-04T23:00:00.000Z

 new Date('2019/04/16'), // 2019-04-15T22:00:00.000Z
 new Date('2019/04/16 '), // 2019-04-15T22:00:00.000Z
 
]);

According to the Date docs, new Date(<string>) invokes Date.parse to get the time value. Besides that, the docs don't seem to give any pointers to what happens to untrimmed strings.

I'm really stuck on this one! Why do space affect the time? It's programming, not general relativity!

_{The console logs above where produced by a Chrome 73 browser running a v8 engine in Berlin (UTC+1)}

javascript date

share|improve this question

asked Mar 26 at 20:32

Nino FiliuNino Filiu

4,28255 gold badges1717 silver badges3434 bronze badges

marked as duplicate by RobG date
Users with the  date badge can single-handedly close date questions as duplicates and reopen them as needed.

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Mar 27 at 0:29

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  Looks like only strict formats are considered as UTC times, and sloppy formats (such as including a space) are parsed according to the local timezone.
  
  – Bergi
  Mar 26 at 20:34
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  That seems indeed to be the answer. Still, that's a very unintuitive design
  
  – Nino Filiu
  Mar 26 at 20:41
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Why would spaces in date strings be considered intuitive? Validate your input first. Note that not all of those formats will work consistently cross browser also
  
  – charlietfl
  Mar 26 at 20:46
  
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  It's not the spaces that are unintuitive, it's the fact that JS decides to chose a different time zone based on the sloppiness of the input. They shouldn't be linked together IMO
  
  – Nino Filiu
  Mar 26 at 20:49
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  @NinoFiliu Well yes, the design of the parser isn't really good, but that how it is and can hardly be changed for webcompat reasons. And this is the exact (and only) reason why using Date.parse to create dates from strings is usually a bad idea in JavaScript (that is, unless you include a timezone signifier explicitly).
  
  – Bergi
  Mar 26 at 20:57
  
  

  
  
  
  

 | 
show 2 more comments

0

This question already has an answer here:

• 
  Why does Date.parse give incorrect results?
  
  11 answers
  
  

I know that creating a date from string is usually a bad idea, but still, this caught my attention: adding a space before or after the date string can affect the created date value.

console.log([

 new Date('2019-03'), // 2019-03-01T00:00:00.000Z
 new Date('2019-03 '), // 2019-02-28T23:00:00.000Z
 new Date(' 2019-03'), // 2019-02-28T23:00:00.000Z

 new Date('2019-03-05'), // 2019-03-05T00:00:00.000Z
 new Date('2019-03-05 '), // 2019-03-04T23:00:00.000Z

 new Date('2019/04/16'), // 2019-04-15T22:00:00.000Z
 new Date('2019/04/16 '), // 2019-04-15T22:00:00.000Z
 
]);

According to the Date docs, new Date(<string>) invokes Date.parse to get the time value. Besides that, the docs don't seem to give any pointers to what happens to untrimmed strings.

I'm really stuck on this one! Why do space affect the time? It's programming, not general relativity!

_{The console logs above where produced by a Chrome 73 browser running a v8 engine in Berlin (UTC+1)}

javascript date

share|improve this question

asked Mar 26 at 20:32

Nino FiliuNino Filiu

4,28255 gold badges1717 silver badges3434 bronze badges

marked as duplicate by RobG date
Users with the  date badge can single-handedly close date questions as duplicates and reopen them as needed.

StackExchange.ready(function()
if (StackExchange.options.isMobile) return;

$('.dupe-hammer-message-hover:not(.hover-bound)').each(function()
var $hover = $(this).addClass('hover-bound'),
$msg = $hover.siblings('.dupe-hammer-message');

$hover.hover(
function()
$hover.showInfoMessage('',
messageElement: $msg.clone().show(),
transient: false,
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StackExchange.helpers.removeMessages();

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Mar 27 at 0:29

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  Looks like only strict formats are considered as UTC times, and sloppy formats (such as including a space) are parsed according to the local timezone.
  
  – Bergi
  Mar 26 at 20:34
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  That seems indeed to be the answer. Still, that's a very unintuitive design
  
  – Nino Filiu
  Mar 26 at 20:41
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Why would spaces in date strings be considered intuitive? Validate your input first. Note that not all of those formats will work consistently cross browser also
  
  – charlietfl
  Mar 26 at 20:46
  
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  It's not the spaces that are unintuitive, it's the fact that JS decides to chose a different time zone based on the sloppiness of the input. They shouldn't be linked together IMO
  
  – Nino Filiu
  Mar 26 at 20:49
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  @NinoFiliu Well yes, the design of the parser isn't really good, but that how it is and can hardly be changed for webcompat reasons. And this is the exact (and only) reason why using Date.parse to create dates from strings is usually a bad idea in JavaScript (that is, unless you include a timezone signifier explicitly).
  
  – Bergi
  Mar 26 at 20:57
  
  

  
  
  
  

 | 
show 2 more comments

This question already has an answer here:

• 
  Why does Date.parse give incorrect results?
  
  11 answers
  
  

I know that creating a date from string is usually a bad idea, but still, this caught my attention: adding a space before or after the date string can affect the created date value.

console.log([

 new Date('2019-03'), // 2019-03-01T00:00:00.000Z
 new Date('2019-03 '), // 2019-02-28T23:00:00.000Z
 new Date(' 2019-03'), // 2019-02-28T23:00:00.000Z

 new Date('2019-03-05'), // 2019-03-05T00:00:00.000Z
 new Date('2019-03-05 '), // 2019-03-04T23:00:00.000Z

 new Date('2019/04/16'), // 2019-04-15T22:00:00.000Z
 new Date('2019/04/16 '), // 2019-04-15T22:00:00.000Z
 
]);

According to the Date docs, new Date(<string>) invokes Date.parse to get the time value. Besides that, the docs don't seem to give any pointers to what happens to untrimmed strings.

I'm really stuck on this one! Why do space affect the time? It's programming, not general relativity!

_{The console logs above where produced by a Chrome 73 browser running a v8 engine in Berlin (UTC+1)}

javascript date

share|improve this question

asked Mar 26 at 20:32

Nino FiliuNino Filiu

4,28255 gold badges1717 silver badges3434 bronze badges

console.log([

 new Date('2019-03'), // 2019-03-01T00:00:00.000Z
 new Date('2019-03 '), // 2019-02-28T23:00:00.000Z
 new Date(' 2019-03'), // 2019-02-28T23:00:00.000Z

 new Date('2019-03-05'), // 2019-03-05T00:00:00.000Z
 new Date('2019-03-05 '), // 2019-03-04T23:00:00.000Z

 new Date('2019/04/16'), // 2019-04-15T22:00:00.000Z
 new Date('2019/04/16 '), // 2019-04-15T22:00:00.000Z
 
]);

console.log([

 new Date('2019-03'), // 2019-03-01T00:00:00.000Z
 new Date('2019-03 '), // 2019-02-28T23:00:00.000Z
 new Date(' 2019-03'), // 2019-02-28T23:00:00.000Z

 new Date('2019-03-05'), // 2019-03-05T00:00:00.000Z
 new Date('2019-03-05 '), // 2019-03-04T23:00:00.000Z

 new Date('2019/04/16'), // 2019-04-15T22:00:00.000Z
 new Date('2019/04/16 '), // 2019-04-15T22:00:00.000Z
 
]);

console.log([

 new Date('2019-03'), // 2019-03-01T00:00:00.000Z
 new Date('2019-03 '), // 2019-02-28T23:00:00.000Z
 new Date(' 2019-03'), // 2019-02-28T23:00:00.000Z

 new Date('2019-03-05'), // 2019-03-05T00:00:00.000Z
 new Date('2019-03-05 '), // 2019-03-04T23:00:00.000Z

 new Date('2019/04/16'), // 2019-04-15T22:00:00.000Z
 new Date('2019/04/16 '), // 2019-04-15T22:00:00.000Z
 
]);

share|improve this question

asked Mar 26 at 20:32

Nino FiliuNino Filiu

4,28255 gold badges1717 silver badges3434 bronze badges

share|improve this question

asked Mar 26 at 20:32

Nino FiliuNino Filiu

4,28255 gold badges1717 silver badges3434 bronze badges

asked Mar 26 at 20:32

Nino FiliuNino Filiu

4,28255 gold badges1717 silver badges3434 bronze badges

asked Mar 26 at 20:32

Nino FiliuNino Filiu

4,28255 gold badges1717 silver badges3434 bronze badges

1 Answer
1

active

oldest

votes

2

From the specification (paragraph 20.3.3.2):

The function first attempts to parse the format of the String
according to the rules (including extended years) called out in Date
Time String Format (20.3.1.16). If the String does not conform to that
format the function may fall back to any implementation-specific
heuristics or implementation-specific date formats.

So, when a space is added, the string does not conform to the Date Time String Format and the parser falls back to implementation-specific algorithm. Like Bergi writes, this takes the local timezone in account.

share|improve this answer

answered Mar 26 at 20:51

edwinedwin

2,1591515 silver badges1515 bronze badges

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  "… this takes the local timezone in account" that is not part of the specification. 2019-03-05 should be parsed as local, but the OP's results show it's being parsed as UTC. So even when the string does conform to ECMA-262, some parsers still get it wrong. And if it doesn't conform to ECMA-262, it's not necessarily parsed as local or UTC, it's up to the implementation. ;-)
  
  – RobG
  Mar 27 at 6:22
  

  
  
  
  

add a comment | 

2

From the specification (paragraph 20.3.3.2):

The function first attempts to parse the format of the String
according to the rules (including extended years) called out in Date
Time String Format (20.3.1.16). If the String does not conform to that
format the function may fall back to any implementation-specific
heuristics or implementation-specific date formats.

So, when a space is added, the string does not conform to the Date Time String Format and the parser falls back to implementation-specific algorithm. Like Bergi writes, this takes the local timezone in account.

share|improve this answer

answered Mar 26 at 20:51

edwinedwin

2,1591515 silver badges1515 bronze badges

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  "… this takes the local timezone in account" that is not part of the specification. 2019-03-05 should be parsed as local, but the OP's results show it's being parsed as UTC. So even when the string does conform to ECMA-262, some parsers still get it wrong. And if it doesn't conform to ECMA-262, it's not necessarily parsed as local or UTC, it's up to the implementation. ;-)
  
  – RobG
  Mar 27 at 6:22
  

  
  
  
  

add a comment | 

2

From the specification (paragraph 20.3.3.2):

The function first attempts to parse the format of the String
according to the rules (including extended years) called out in Date
Time String Format (20.3.1.16). If the String does not conform to that
format the function may fall back to any implementation-specific
heuristics or implementation-specific date formats.

So, when a space is added, the string does not conform to the Date Time String Format and the parser falls back to implementation-specific algorithm. Like Bergi writes, this takes the local timezone in account.

share|improve this answer

answered Mar 26 at 20:51

edwinedwin

2,1591515 silver badges1515 bronze badges

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  "… this takes the local timezone in account" that is not part of the specification. 2019-03-05 should be parsed as local, but the OP's results show it's being parsed as UTC. So even when the string does conform to ECMA-262, some parsers still get it wrong. And if it doesn't conform to ECMA-262, it's not necessarily parsed as local or UTC, it's up to the implementation. ;-)
  
  – RobG
  Mar 27 at 6:22
  

  
  
  
  

add a comment | 

From the specification (paragraph 20.3.3.2):

The function first attempts to parse the format of the String
according to the rules (including extended years) called out in Date
Time String Format (20.3.1.16). If the String does not conform to that
format the function may fall back to any implementation-specific
heuristics or implementation-specific date formats.

So, when a space is added, the string does not conform to the Date Time String Format and the parser falls back to implementation-specific algorithm. Like Bergi writes, this takes the local timezone in account.

share|improve this answer

answered Mar 26 at 20:51

edwinedwin

2,1591515 silver badges1515 bronze badges

share|improve this answer

answered Mar 26 at 20:51

edwinedwin

2,1591515 silver badges1515 bronze badges

answered Mar 26 at 20:51

edwinedwin

2,1591515 silver badges1515 bronze badges

answered Mar 26 at 20:51

edwinedwin

2,1591515 silver badges1515 bronze badges