Generating a Date from a String with a 'Month-Year' Format

Generating a date from a string with a 'Month-Year' format

You've got it backwards:

library(zoo)
as.yearmon(date, format="%b-%y")
# [1] "Jan 2010" "Feb 2010" "Mar 2010" "Jun 2010" "Jul 2010"

Specify the format in the order in which it appears in the input.

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Do not just arbitrarily specify the date format. Note what your attempts were looking for:

• "%m/%d/%Y" does not work because that is expecting dates in the form of "10/31/2013"
• "%y-%b" does not work because that is expecting dates in the form of "13-Oct"

Converting year and month (yyyy-mm format) to a date?

Try this. (Here we use text=Lines to keep the example self contained but in reality we would replace it with the file name.)

Lines <- "2009-01  12
2009-02  310
2009-03  2379
2009-04  234
2009-05  14
2009-08  1
2009-09  34
2009-10  2386"

library(zoo)
z <- read.zoo(text = Lines, FUN = as.yearmon)
plot(z)

The X axis is not so pretty with this data but if you have more data in reality it might be ok or you can use the code for a fancy X axis shown in the examples section of ?plot.zoo .

The zoo series, z, that is created above has a "yearmon" time index and looks like this:

> z
Jan 2009 Feb 2009 Mar 2009 Apr 2009 May 2009 Aug 2009 Sep 2009 Oct 2009 
      12      310     2379      234       14        1       34     2386 

"yearmon" can be used alone as well:

> as.yearmon("2000-03")
[1] "Mar 2000"

Note:

1. "yearmon" class objects sort in calendar order.

2. This will plot the monthly points at equally spaced intervals which is likely what is wanted; however, if it were desired to plot the points at unequally spaced intervals spaced in proportion to the number of days in each month then convert the index of z to "Date" class: time(z) <- as.Date(time(z)) .

String to date, but only month and year

Let's say your dataframe looks like this

import pandas as pd
df = pd.DataFrame({'date':['2021-01','2021-02','2021-03','2021-04']})

Option 1: dates as pd.Period

df['date_period'] = pd.to_datetime(df['date'],format='%Y-%m').dt.to_period('M')

You can access years and months via

df['year'] = df['date_period'].dt.year
df['month'] = df['date_period'].dt.month

Option 2: dates as integer

df['date_int'] = df['date'].str.replace('-','').astype(int)

You can access years and months via

df['year'] = df['date_int'] // 100
df['month'] = df['date_int'] % 100

Comparison

The result looks like this:

      date date_period  date_int
0  2021-01     2021-01    202101
1  2021-02     2021-02    202102
2  2021-03     2021-03    202103
3  2021-04     2021-04    202104

The second option is approximately twice as fast as the first one:

%timeit pd.to_datetime(df['date'],format='%Y-%m').dt.to_period('M')

703 µs ± 78.7 µs per loop (mean ± std. dev. of 7 runs, 1000 loops each)

%timeit df['date'].str.replace('-','').astype(int)

304 µs ± 8.2 µs per loop (mean ± std. dev. of 7 runs, 1000 loops each)

Java: Convert String Date to Month Name Year (MMM yyyy)

Your format must match your input

for 2016-03-20

the format should be (just use a second SimpleDateFormat object)

SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");

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Full answer

SimpleDateFormat month_date = new SimpleDateFormat("MMM yyyy", Locale.ENGLISH);
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");

String actualDate = "2016-03-20";

Date date = sdf.parse(actualDate);

String month_name = month_date.format(date);
System.out.println("Month :" + month_name);  //Mar 2016

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Using java.time java-8

String actualDate = "2016-03-20";
DateTimeFormatter dtf = DateTimeFormatter.ofPattern("yyyy-MM-dd", Locale.ENGLISH);
DateTimeFormatter dtf2 = DateTimeFormatter.ofPattern("MMM yyyy", Locale.ENGLISH);
DateTimeFormatter dtf3 = DateTimeFormatter.ofPattern("MMMM yyyy", Locale.ENGLISH);
LocalDate ld = LocalDate.parse(actualDate, dtf);
String month_name = dtf2.format(ld);
System.out.println(month_name); // Mar 2016
String fullMonthAndYear = dtf3.format(ld);
System.out.println(fullMonthAndYear); // March 2016

How to convert year-month-day date format(eg: 2015-05-12-which is a value retrieved from server) to day-month-year format in android

First you'll need to parse the String into a Date. Then you format the date according to your needs, the example below is an edited version of BalusC's answer from this topic: Change date format in a Java string

String oldstring = "2015-05-12";
Date date = new SimpleDateFormat("yyyy-MM-dd").parse(oldstring);
//Use SimpleDateFormat#format() to format a Date into a String in a certain pattern.

String newstring = new SimpleDateFormat("dd-MM-yyyy").format(date);
System.out.println(newstring); // 12-05-2015

How to Convert (Year, Month, Day) into the Expanded-Year Date Format in Javascript with the Handling for Years 0 to 99

It's a legacy feature that the constructor treats year values from 0 to 99 as 1900 + year, there's no fixing that until the Temporal object is implemented (which might be in ECMAScript 2023 as it seems imminent but it's not in the latest ECMA-262 2022 draft).

As for formatting, ECMAScript has very limited formatting support for dates, which is why there are so many date libraries. You can do a combination of an existing formatting method or create an entirely new one.

E.g. if only positive years are required, then you can leverage toLocaleDateString:

console.log(
  new Date()
      .toLocaleDateString('en-CA')
      .replace(/^(.\d+)/,y => (y<0? '-' : '+')+(''+Math.abs(y))
      .padStart(6,'0'))
);

Swift: Date string only has month and year, can I still produce a date?

You almost had it, I tested it on playgrounds use it like this(Just changed the "yyyy-MM" part):

var date = "2001-05"

func stringToDate(_ date: String) -> Date? {
    let df = DateFormatter()
    df.locale = NSLocale(localeIdentifier: "en_US_POSIX") as Locale!
    df.dateFormat = "yyyy-MM"
    df.date(from: date)

    return df.date(from: date)
}

print(stringToDate(date)!)

Java - Format a date given day, month and year integers

If you're concerned about garbage collecting and objects creation, why not keep a single Calendar instance in your class or system, and use it for all formatting purposes using a static / synchronized method?

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