## Class DateMath

• ```public class DateMath
extends Object```
Provides a utility for calculating relative dates. The class calculates a date based upon an expression. The syntax of the expression is given below.

Date Expression

```       <expression>     := <expression>+ ( ';' DATESPEC )?
<expression>     := OPERATION? OPERAND ':' <unit> <position>?
<unit>           := 'Y' | 'M' | 'D' | 'W' | 'h' | 'm' | 's'
<position>       := 'S' | 'E'
OPERATION        := '+' | '-'
OPERAND          := [0..9]+
DATESPEC         := <i>any `SimpleDateFormat` format pattern</i>
```
The OPERAND specifies the positive or negative offset to the date. The unit inidcates the unit of the date to manipulate. The optional position indicates the relative position for the specified unit: S for start and E for end. The following are the valid unit values.
```       Y        Year
M        Month
W        Week
D        Day
h        hour
m        minute
s        second
```

Examples:

```       0:ME -1:DS       00:00:00.000 of the day before the last day of the current month
0:MS  0:WE       23:59:59.999 the last day of the first week of the month
0:ME             23:59:59.999 of the last day of the current month
5:Y              the current month, day and time 5 years in the future
5:YS             00:00:00.000 of the first day of the years 5 years in the future
```
• ### Constructor Summary

Constructors
Constructor Description
`DateMath()`
• ### Method Summary

All Methods
Modifier and Type Method Description
`static Calendar` `calculateDate​(String expression)`
Calculates the date specified by the expression, relative to the current date/time.
`static Calendar` ```calculateDate​(Calendar date, String expression)```
Calculates the date specified by the expression, relative to the indicated date/time.
`static String` ```calculateDateString​(Calendar date, String expressionWithFormat)```
Calculates a date, returning the formatted string version of the calculated date.
`static String` ```calculateDateString​(Calendar date, String expressionWithFormat, Locale locale)```
Calculates a date, returning the formatted string version of the calculated date.
`static String` `claculateDateString​(String expressionWithFormat)`
Calculates a date, returning the formatted string version of the calculated date.
• ### Methods inherited from class java.lang.Object

`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`
• ### Constructor Detail

• #### DateMath

`public DateMath()`
• ### Method Detail

• #### claculateDateString

`public static String claculateDateString​(String expressionWithFormat)`
Calculates a date, returning the formatted string version of the calculated date. The method is a short cut for `calculateDate(null,expressionWithFormat,null)`. If the date format is omitted, the short format for the `PentahoSystem#getLocale()` is used.
Parameters:
`expressionWithFormat` - the relative date expression with optional format specification.
Returns:
The calculated date as a string.
Throws:
`IllegalArgumentException` - if expressionWithFormat is invalid.
• #### calculateDateString

```public static String calculateDateString​(Calendar date,
String expressionWithFormat)```
Calculates a date, returning the formatted string version of the calculated date. The method is a short cut for `calculateDate(date,expressionWithFormat,null)`.
Parameters:
`date` - the target date against the expression will be applied.
`expressionWithFormat` - the relative date expression with optional format specification.
Returns:
The calculated date as a string.
Throws:
`IllegalArgumentException` - if expressionWithFormat is invalid.
• #### calculateDateString

```public static String calculateDateString​(Calendar date,
String expressionWithFormat,
Locale locale)```
Calculates a date, returning the formatted string version of the calculated date.
Parameters:
`date` - the target date against the expression will be applied. If null, the current date is used.
`expressionWithFormat` - the relative date expression with optional format specification.
`locale` - the desired locale for the formatted string.
Returns:
The calculated date as a string.
Throws:
`IllegalArgumentException` - if expressionWithFormat is invalid.
• #### calculateDate

`public static Calendar calculateDate​(String expression)`
Calculates the date specified by the expression, relative to the current date/time. The method is a short cut for `calculate(null,expression)`.
Parameters:
`expression` - the date expression as described above.
Returns:
The calculated date.
Throws:
`IllegalArgumentException` - if expression is invalid.
• #### calculateDate

```public static Calendar calculateDate​(Calendar date,
String expression)```
Calculates the date specified by the expression, relative to the indicated date/time.
Parameters:
`date` - the target date against the expression is evaluated. If null, the current date/time is used. If not null, the object is manipulated by the expression.
`expression` - the date expression as described above.
Returns:
The calculated date. This will be date if date is not null.