CODEWITHSUNDEEP
androiddate
Femn Dharamshi
Femn Dharamshi

Reputation: 577

check if saved date is one day before to current date android

Okay so i read this : Check date with todays date

@sudocode gave this code : 

Calendar c = Calendar.getInstance();

// set the calendar to start of today
c.set(Calendar.HOUR_OF_DAY, 0);
c.set(Calendar.MINUTE, 0);
c.set(Calendar.SECOND, 0);
c.set(Calendar.MILLISECOND, 0);

// and get that as a Date
Date today = c.getTime();

// or as a timestamp in milliseconds
long todayInMillis = c.getTimeInMillis();

// user-specified date which you are testing
// let's say the components come from a form or something
int year = 2011;
int month = 5;
int dayOfMonth = 20;

// reuse the calendar to set user specified date
c.set(Calendar.YEAR, year);
c.set(Calendar.MONTH, month);
c.set(Calendar.DAY_OF_MONTH, dayOfMonth);

// and get that as a Date
Date dateSpecified = c.getTime();

// test your condition
if (dateSpecified.before(today)) {
  System.err.println("Date specified [" + dateSpecified + "] is before today [" + today + "]");
} else {
  System.err.println("Date specified [" + dateSpecified + "] is NOT before today [" + today + "]");
}

But imagine the saved date was 28/01/2018 11:00pm and i run this at 28/01/2018 11:15pm so this code will tell me that saved date is before the current date.

What i want is, the code should only run a function if the saved date is more than one day old... (not 24 hours but actually a day or more old) lets say saved date it 27/01/2018 11:00pm and current date is 28/01/2018 then it should run.. how do i implement this ?

Upvotes: 1

Views: 2672

Answers (2)

Basil Bourque
Basil Bourque

Reputation: 339332

tl;dr

Determining dates requires a time zone.

Use only java.time classes, never legacy java.util.Date, Calendar, java.sql.Date, java.sql.Timestamp, etc.

myResultSet.getObject( 
    … , 
    Instant.class 
)                          // Retrieve a `java.time.Instant` from a column of type akin to the SQL-standard `TIMESTAMP WITH TIME ZONE`. 
.atZone(
    ZoneId.of( "Pacific/Auckland" ) 
)
.toLocalDate()
.isEqual( 
    LocalDate.now( ZoneId.of( "Pacific/Auckland" ) )
)

Avoid legacy date-time classes

The terrible Date and Calendar legacy classes were supplanted years ago by the modern java.time classes.

Time zones

Your Question ignores the crucial issue of time zone. For any given moment, the date and time-of-day both vary around the globe by time zone. You cannot talk about dates without talking about time zone. For example, a few minutes after midnight in Paris France is a new day while still “yesterday” in Montréal Québec.

If no time zone is specified, the JVM implicitly applies its current default time zone. That default may change at any moment during runtime(!), so your results may vary. Better to specify your [desired/expected time zone][2] explicitly as an argument.

Specify a proper time zone name in the format of continent/region, such as America/Montreal, Africa/Casablanca, or Pacific/Auckland. Never use the 3-4 letter abbreviation such as EST or IST as they are not true time zones, not standardized, and not even unique(!). 

ZoneId z = ZoneId.of( "America/Montreal" ) ;  
LocalDate today = LocalDate.now( z ) ;

If you want to use the JVM’s current default time zone, ask for it and pass as an argument. If omitted, the JVM’s current default is applied implicitly. Better to be explicit, as the default may be changed at any moment during runtime by any code in any thread of any app within the JVM.

ZoneId z = ZoneId.systemDefault() ;  // Get JVM’s current default time zone.

Or specify a date. You may set the month by a number, with sane numbering 1-12 for January-December. 

LocalDate ld = LocalDate.of( 1986 , 2 , 23 ) ;  // Years use sane direct numbering (1986 means year 1986). Months use sane numbering, 1-12 for January-December.

Or, better, use the Month enum objects pre-defined, one for each month of the year. Tip: Use these Month objects throughout your codebase rather than a mere integer number to make your code more self-documenting, ensure valid values, and provide type-safety.

LocalDate ld = LocalDate.of( 1986 , Month.FEBRUARY , 23 ) ;

Never assume 00:00:00

Also, do not assume the day starts at 00:00:00. Because of anomalies such as Daylight Saving Time (DST), the day may start at another time, such as 01:00:00. Let java.time determine the first moment of the day. Specify a time zone to yield a ZonedDateTime object representing a specific moment.

ZonedDateTime startOfToday = LocalDate.now( z ).atStartOfDay( z ) ;
ZonedDateTime startOfYesterday = startOfToday.toLocalDate().minusDays( 1 ).atStartOfDay( z ) ;

For querying database, it is often best to use UTC values. To adjust from our time zone to UTC, simply extract a Instant.

Instant start = startOfToday.toInstant() ;
Instant stop = startOfYesterday.toInstant() ;

Ready to query database. Using Half-Open approach here where beginning is inclusive while ending is exclusive. So, do not use SQL BETWEEN.

// SQL for SELECT WHERE when_field >= ? AND when_field < ? 
myPreparedStatement.setObject( 1 , start ) ;
myPreparedStatement.setObject( 2 , stop ) ;

Comparing dates

If you just want to check the age of a retrieved moment, retrieve an Instant.

Instant instant = myResultSet.getObject( … , Instant.class ) ;

Apply a time zone to get a ZonedDateTime. Then extract the date-only value.

ZonedDateTime zdt = instant.atZone( z ) ;
LocalDate ld = zdt.toLocalDate() ;  // Extract the date-only value.

Compare to today's date.

LocalDate yesterday = LocalDate.now( z ).minusDays( 1 ) ;  // Subtract one day from today to get yesterday.
Boolean retrievedDateIsYesterday = ld.isEqual( yesterday ) ;

If you work much with spans-of-time, see the Interval and LocalDateRange classes in the ThreeTen-Extra project linked below.

About java.time

The java.time framework is built into Java 8 and later. These classes supplant the troublesome old legacy date-time classes such as java.util.Date, Calendar, & SimpleDateFormat.

The Joda-Time project, now in maintenance mode, advises migration to the java.time classes.

To learn more, see the Oracle Tutorial. And search Stack Overflow for many examples and explanations. Specification is JSR 310.

You may exchange java.time objects directly with your database. Use a JDBC driver compliant with JDBC 4.2 or later. No need for strings, no need for java.sql.* classes.

Where to obtain the java.time classes?

The ThreeTen-Extra project extends java.time with additional classes. This project is a proving ground for possible future additions to java.time. You may find some useful classes here such as Interval, YearWeek, YearQuarter, and more.

Upvotes: 1

brf42
brf42

Reputation: 151

You can do something like this:

public long daysBetween(Calendar first, Calendar second) {
    long diffInMillis = second.getTimeInMillis() - first.getTimeInMillis();
    return TimeUnit.MILLISECONDS.toDays(diffInMillis);
}

And then just ask if the difference is >= 1. This also assumes that second >= first.

This example is using the standard Java (7) date stuff, so you should be able to use it in your project.

Upvotes: 2

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