Convert Date-Time String to Class Date

Convert datetime object to a String of date only in Python

You can use strftime to help you format your date.

E.g.,

import datetime
t = datetime.datetime(2012, 2, 23, 0, 0)
t.strftime('%m/%d/%Y')

will yield:

'02/23/2012'

More information about formatting see here

How do I convert a date/time string to a DateTime object in Dart?

DateTime has a parse method

var parsedDate = DateTime.parse('1974-03-20 00:00:00.000');

https://api.dartlang.org/stable/dart-core/DateTime/parse.html

Convert date-time string to class Date

You may be overcomplicating things, is there any reason you need the stringr package? You can use as.Date and its format argument to specify the input format of your string.

 df <- data.frame(Date = c("10/9/2009 0:00:00", "10/15/2009 0:00:00"))
 as.Date(df$Date, format =  "%m/%d/%Y %H:%M:%S")
 # [1] "2009-10-09" "2009-10-15"

Note the Details section of ?as.Date:

Character strings are processed as far as necessary for the format specified: any trailing characters are ignored

Thus, this also works:

as.Date(df$Date, format =  "%m/%d/%Y")
# [1] "2009-10-09" "2009-10-15"

All the conversion specifications that can be used to specify the input format are found in the Details section in ?strptime. Make sure that the order of the conversion specification as well as any separators correspond exactly with the format of your input string.

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More generally and if you need the time component as well, use as.POSIXct or strptime:

as.POSIXct(df$Date, "%m/%d/%Y %H:%M:%S")    
strptime(df$Date, "%m/%d/%Y %H:%M:%S")

I'm guessing at what your actual data might look at from the partial results you give.

Change a Java date-time string to date

You need to use the SimpleDateFormat:

    String sDate = "2018-01-17 00:00:00";
    SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
    Date date = df.parse(sDate);

    SimpleDateFormat df1 = new SimpleDateFormat("dd-MM-yyyy");
    System.out.println(df1.format(date));

Go through the SimpleDateFormat class to get into details for this

Fastest way to parse a date-time string to class Date

Note that as.Date will ignore junk after the date so this takes less than 10 seconds on my not particularly fast laptop:

xx <- rep("10/17/2017 12:00:00 AM", 5000000) # test input
system.time(as.Date(xx, "%m/%d/%Y"))
## user  system elapsed 
## 9.57    0.20    9.82 

how to convert date and time from character to datetime type

As @Richard Scriven pointed out, you shouldn't be using as.Date because it's not a datetime class. Here are a few different ways:

DateTime <- "2007-02-01 00:00:00"
DateTime2 <- "02/01/2007 00:06:10"
## default format Y-m-d H:M:S
> as.POSIXct(DateTime,tz=Sys.timezone())
[1] "2007-02-01 EST"
> as.POSIXlt(DateTime,tz=Sys.timezone())
[1] "2007-02-01 EST"
##
## specify format m/d/Y H:M:S
> as.POSIXct(DateTime2,format="%m/%d/%Y %H:%M:%S",tz=Sys.timezone())
[1] "2007-02-01 00:06:10 EST"
> as.POSIXlt(DateTime2,format="%m/%d/%Y %H:%M:%S",tz=Sys.timezone())
[1] "2007-02-01 00:06:10 EST"
##
## using lubridate
library(lubridate)
> ymd_hms(DateTime,tz=Sys.timezone())
[1] "2007-02-01 EST"
> mdy_hms(DateTime2,tz=Sys.timezone())
[1] "2007-02-01 00:06:10 EST"

You don't have to specify format= for as.POSIXct and as.POSIXlt when you have the %Y-%m-%d %H:%M:%S format. In other cases, like %m/%d/%Y %H:%M:%S, you usually have to specify the format explicitly.

How can I convert a string datetime column to a datetime column in R?

We can just use %T

as.Date(data$timestamp, "%Y-%m-%d %T")
#[1] "2020-08-10" "2020-08-10" "2020-04-15" "2020-01-18" "2020-02-12"

data

data <- structure(list(Id = c("A9", "B9", "G1", "D2", "F8"), timestamp = c("2020-08-10 09:05:01.000000", 
"2020-08-10 09:04:18.000000", "2020-04-15 11:05:08.000000", "2020-01-18 19:04:05.000000", 
"2020-02-12 08:04:08.000000")), class = "data.frame", row.names = c(NA, 
-5L))

converting date time string to date with time in R

Use as.POSIXct or strptime:

as.POSIXct("9/2/11 4:20", format="%m/%d/%y %H:%M",tz="GMT")
#[1] "2011-09-02 04:20:00 GMT"

strptime("9/2/11 4:20", format="%m/%d/%y %H:%M",tz="GMT")
#[1] "2011-09-02 04:20:00 GMT"

Class Date does not contain information on the time of the day by definition.

Java string to date conversion

That's the hard way, and those java.util.Date setter methods have been deprecated since Java 1.1 (1997). Moreover, the whole java.util.Date class was de-facto deprecated (discommended) since introduction of java.time API in Java 8 (2014).

Simply format the date using DateTimeFormatter with a pattern matching the input string (the tutorial is available here).

In your specific case of "January 2, 2010" as the input string:

1. "January" is the full text month, so use the MMMM pattern for it
2. "2" is the short day-of-month, so use the d pattern for it.
3. "2010" is the 4-digit year, so use the yyyy pattern for it.

String string = "January 2, 2010";
DateTimeFormatter formatter = DateTimeFormatter.ofPattern("MMMM d, yyyy", Locale.ENGLISH);
LocalDate date = LocalDate.parse(string, formatter);
System.out.println(date); // 2010-01-02

Note: if your format pattern happens to contain the time part as well, then use LocalDateTime#parse(text, formatter) instead of LocalDate#parse(text, formatter). And, if your format pattern happens to contain the time zone as well, then use ZonedDateTime#parse(text, formatter) instead.

Here's an extract of relevance from the javadoc, listing all available format patterns:

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