Top Most How to add, subtract days, months, years, hours from Date and Time in Java

Adding days, hours, month or years to dates is a common task in Java. java.util.Calendar can be used to perform Date and Time arithmetic in Java. Calendar class not only provides date manipulation but it also support time manipulation i.e. you can add, subtract hours, minutes and seconds from current time. Calendar class automatically handles date transition or month transition for example if you ask date after 30 days it will return you date based on whether current month is 30 or 31 days long. Same is true in case of adding and subtracting years, Calendar takes care whether current or following year is a leap year or not. For example 2012 is a leap year and it has February with 29 days, if you ask Calendar day before 365 it will return 24th July (assuming current date 23^rd July) which shows it take care of leap year. By the way there are couple of more date and time related articles e.g. How to find current date and time in Java and How to convert Date to String in Java. If you haven’t read them already, It’s worth checking to know more about Date and Time in Java.

Read more »

Top Most How to convert milliseconds to Date in Java - tutorial example

Do you want to convert milliseconds to Date in Java ? Actually java.util.Date is internally specified in milliseconds from epoch. So any date is number of millisecond passed since January 1, 1970, 00:00:00 GMT and Date provides constructorwhich can be used to create Date from milliseconds. Knowing the fact that Date is internally maintained in milliseconds allows you to store date in form of millisecond in Server or in your Classbecause that can be effectively expressed with a long value. In fact many experienced Java programmer store Date as long value while writing Immutable class which requires Date, one of the reason for that is Date being mutable and long value of Date can be very handy. By the ways this is next in Date related article, we have already discussed How to convert String to Date and How to get current month, year and day of week from Date in Java. If you haven’t read them already, you may find them useful. In this Java tutorial we will see example of converting millisecond into Date in Java.

Read more »

Top Most How to get current date, month, year and day of week in Java program

Here is quick Java tip to get current date, month, year and day of week from Java program. Java provides a rich Date and Time API though having thread-safety issue but its rich in function and if used locally can give you all the date and time information which you need for your enterprise Java application. In last Java tutorial on Date and Time API we have seen how to get current date and time from different timezone using DateFormat and SimpleDateFormat classes and in this post we will get some more details like current month, year, day of week etc by using java.util.Calendar class.  Just keep in mind that Calendar instance should not be shared between multiple threads. Calendar class in Java provides different fields to get different information e.g. Calendar.DATE gives you current date while Calendar.MONTH gives you current month based on what type of Calendar you are using, which depends upon locale.

Read more »

Top Most How to increment decrement date by days in Java - Tutorial example

While working in Java projects, we often needs to increment or decrement date e.g. adding one days to current date to get tomorrow's date, subtracting one day to get yesterday's date etc. Since date in Java is maintained as long millisecond value, Sometime, programmer tend to add 24 hours as one day, which could be wrong if day falls on a day light saving time zone, where a day could be either 23 or 25 hour long. When you add or subtract days from date, other components' of date e.g. month and year must roll. In this Java date tutorial, we will see two ways to increment and decrement date in Java. One approach uses java.util.Calendar from JDK and other uses DateUtils class from Apache commons lang library. DateUtils class provides convenient addDays(Date, int days) method, which accept a date and number of days to add, you can subtract days by passing negative value. Similarly java.util.Calendar provides Calendar.add() method, which accept a calendar field, for adding days, you need to use Calendar.DAY_OF_MONTH. Similar to DateUtils, you can pass positive number to increment date, and negative integer to decrement date in Java.

Read more »