java.lang.Object
- org.apache.solr.util.DateMathParser

```
public class DateMathParser
extends Object
```
A Simple Utility class for parsing "math" like strings relating to Dates.
The basic syntax support addition, subtraction and rounding at various levels of granularity (or "units"). Commands can be chained together and are parsed from left to right. '+' and '-' denote addition and subtraction, while '/' denotes "round". Round requires only a unit, while addition/subtraction require an integer value and a unit. Command strings must not include white space, but the "No-Op" command (empty string) is allowed....
```
   /HOUR
      ... Round to the start of the current hour
   /DAY
      ... Round to the start of the current day
   +2YEARS
      ... Exactly two years in the future from now
   -1DAY
      ... Exactly 1 day prior to now
   /DAY+6MONTHS+3DAYS
      ... 6 months and 3 days in the future from the start of
          the current day
   +6MONTHS+3DAYS/DAY
      ... 6 months and 3 days in the future from now, rounded
          down to nearest day
 
```
(Multiple aliases exist for the various units of time (ie: MINUTE and MINUTES; MILLI, MILLIS, MILLISECOND, and MILLISECONDS.) The complete list can be found by inspecting the keySet of CALENDAR_UNITS)

All commands are relative to a "now" which is fixed in an instance of DateMathParser such that p.parseMath("+0MILLISECOND").equals(p.parseMath("+0MILLISECOND")) no matter how many wall clock milliseconds elapse between the two distinct calls to parse (Assuming no other thread calls "setNow" in the interim). The default value of 'now' is the time at the moment the DateMathParser instance is constructed, unless overridden by the NOW request param.

All commands are also affected to the rules of a specified TimeZone (including the start/end of DST if any) which determine when each arbitrary day starts. This not only impacts rounding/adding of DAYs, but also cascades to rounding of HOUR, MIN, MONTH, YEAR as well. The default TimeZone used is UTC unless overridden by the TZ request param.

Historical dates: The calendar computation is completely done with the Gregorian system/algorithm. It does not switch to Julian or anything else, unlike the default GregorianCalendar.
See Also:

SolrRequestInfo.getClientTimeZone(), SolrRequestInfo.getNOW()

Field Summary

Fields
Modifier and Type	Field	Description
`static Map<String,ChronoUnit>`	`CALENDAR_UNITS`	A mapping from (uppercased) String labels identifying time units, to the corresponding `ChronoUnit` enum (e.g.
`static TimeZone`	`DEFAULT_MATH_TZ`	Default TimeZone for DateMath rounding (UTC)
`static DateTimeFormatter`	`PARSER`	Differs by `DateTimeFormatter.ISO_INSTANT` in that it's lenient.
`static TimeZone`	`UTC`

Constructor Summary

Constructors
Constructor	Description
`DateMathParser()`	Chooses defaults based on the current request.
`DateMathParser(Date now, TimeZone tz)`
`DateMathParser(TimeZone tz)`

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`Date`	`getNow()`	Returns a clone of this instance's concept of "now" (never null).
`TimeZone`	`getTimeZone()`
`Date`	`parseMath(String math)`	Parses a string of commands relative "now" are returns the resulting Date.
`static Date`	`parseMath(Date now, String val)`	Parses a String which may be a date (in the standard ISO-8601 format) followed by an optional math expression.
`static Date`	`parseMath(Date now, String val, TimeZone zone)`	Parses a String which may be a date (in the standard ISO-8601 format) followed by an optional math expression.
`void`	`setNow(Date n)`	Defines this instance's concept of "now".

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - UTC
```
public static final TimeZone UTC
```
  - DEFAULT_MATH_TZ
```
public static final TimeZone DEFAULT_MATH_TZ
```
    Default TimeZone for DateMath rounding (UTC)
  - PARSER
```
public static final DateTimeFormatter PARSER
```
    Differs by DateTimeFormatter.ISO_INSTANT in that it's lenient.
    
    See Also:
    
    parseNoMath(String)
  - CALENDAR_UNITS
```
public static final Map<String,ChronoUnit> CALENDAR_UNITS
```
    A mapping from (uppercased) String labels identifying time units, to the corresponding ChronoUnit enum (e.g. "YEARS") used to set/add/roll that unit of measurement.
    A single logical unit of time might be represented by multiple labels for convenience (ie: DATE==DAYS, MILLI==MILLIS)
    
    See Also:
    
    Calendar
- Constructor Detail
  - DateMathParser
```
public DateMathParser()
```
    Chooses defaults based on the current request.
    
    See Also:
    
    SolrRequestInfo.getClientTimeZone(), SolrRequestInfo.getNOW()
  - DateMathParser
```
public DateMathParser(TimeZone tz)
```
  - DateMathParser
```
public DateMathParser(Date now,
                      TimeZone tz)
```
    Parameters:
    
    now - The current time. If null, it defaults to SolrRequestInfo.getNOW(). otherwise the current time is assumed.
    
    tz - The TimeZone used for rounding (to determine when hours/days begin). If null, then this method defaults to the value dictated by the SolrRequestInfo if it exists -- otherwise it uses UTC.
    
    See Also:
    
    DEFAULT_MATH_TZ, Calendar.getInstance(TimeZone,Locale), SolrRequestInfo.getClientTimeZone()
- Method Detail
  - parseMath
```
public static Date parseMath(Date now,
                             String val)
```
    Parses a String which may be a date (in the standard ISO-8601 format) followed by an optional math expression. The TimeZone is taken from the TZ param retrieved via SolrRequestInfo, defaulting to UTC.
    
    Parameters:
    
    now - an optional fixed date to use as "NOW". SolrRequestInfo is consulted if unspecified.
    
    val - the string to parse
  - parseMath
```
public static Date parseMath(Date now,
                             String val,
                             TimeZone zone)
```
    Parses a String which may be a date (in the standard ISO-8601 format) followed by an optional math expression.
    
    Parameters:
    
    now - an optional fixed date to use as "NOW"
    
    val - the string to parse
    
    zone - the timezone to use
  - getTimeZone
```
public TimeZone getTimeZone()
```
    Returns:
    
    the time zone
  - setNow
```
public void setNow(Date n)
```
    Defines this instance's concept of "now".
    
    See Also:
    
    getNow()
  - getNow
```
public Date getNow()
```
    Returns a clone of this instance's concept of "now" (never null). If setNow was never called (or if null was specified) then this method first defines 'now' as the value dictated by the SolrRequestInfo if it exists -- otherwise it uses a new Date instance at the moment getNow() is first called.
    
    See Also:
    
    setNow(java.util.Date), SolrRequestInfo.getNOW()
  - parseMath
```
public Date parseMath(String math)
               throws ParseException
```
    Parses a string of commands relative "now" are returns the resulting Date.
    
    Throws:
    
    ParseException - positions in ParseExceptions are token positions, not character positions.

Class DateMathParser

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

UTC

DEFAULT_MATH_TZ

PARSER

CALENDAR_UNITS

Constructor Detail

DateMathParser

DateMathParser

DateMathParser

Method Detail

parseMath

parseMath

getTimeZone

setNow

getNow

parseMath