An RWDateTime may be constructed in several ways. Unlike RWDate and the deprecated RWTime described in Section 3.6 and Section 3.7, the RWDateTime default constructor does not automatically set the time and date to the current time and date. This change provides an efficient way to construct large arrays of RWDateTime. The current time and date can still be set by using a constructor. Simply include the enum RWDateTime::setCurrentTime in RWDateTime’s constructor argument list. See the SourcePro C++ API Reference Guide for a complete description of RWDateTime.

For example, to construct an RWDateTime with today’s date and current time, use the following:

An RWDateTime can also be constructed from a given date and/or a given time. Or you can use an RWDateTime constructor that takes a string and the enum RWDateTime::SetType, which indicates whether you are setting a date, a time, or both. By default, the constructor expects to set both the date and time. For example, to construct an RWDateTime for a given date, where time is of no concern, use:

Similarly, to construct an RWDateTime for a given time:

Finally, to construct an RWDateTime for a given date and time, you can use the following techniques. Note that when you initialize both the day and time, the date precedes the time and the two values are separated by a semicolon.

or

The default format for an RWDateTime on many systems and in many locales contains only a two-digit year. Two-digit year specifiers assume the century 1900, so you should create programs that use four-digit year specifiers. You can enforce the use of a four-digit year by defining the build macro RW_CENTURY_REQD in RCB when building the libraries.

Be aware, however, that defining this macro requires a four-digit year to be provided when constructing an RWDateTime. For example, the following code may fail:

The solution is to first convert the RWDateTime to a string using RWDateTime::asString() with a format string suitable for your locale that includes four-digit years. For example, replace line //1 above with:

Class RWDateTime has member functions to compare, store, add, and subtract RWDateTimes. An RWDateTime may return specific time units (days, hours, seconds), or fill a struct tm for any time zone. A complete list of member functions appears in the SourcePro C++ API Reference Guide.

For example, here is a code fragment that outputs the hour in local and UTC (GMT) zones, and then the complete local time and date.

RWDateTime has the ability to hold sentinel values that are not necessarily dates, but are convenient to use as comparison values within applications. For example, a “future” sentinel provides a value that represents a date larger than the largest RWDateTime. RWDateTime currently provides four internal, pre-defined sentinels and can accommodate up to 128 user-defined sentinels. The RWDateTime sentinels are described in the following sections.

Table 3 summarizes the responses of RWDateTime operations when applied to various sentinels. The sections that follow Table 3 provide more information about the sentinels.

The Essential Tools Module allows for RWDateTime instances with an “invalid” state that can be compared to other RWDateTime instances and can be persisted. The default RWDateTime constructor constructs an invalid instance, and other construction techniques are available, including the RWDateTime::invalidSentinel constant. You can pass this constant to the RWDateTime(rwint64) constructor to create instances of the minimum and maximum RWDateTime as needed, or you can use it to compare directly with the millisecond count returned by RWDateTime::milliSeconds().

No other operations work, other than persisting the invalid object and using it in comparisons of equality and inequality. Arithmetic manipulation of an invalid RWDateTime results in an invalid RWDateTime. Attempts to use the part extraction functions (day(), month(), extract(), etc.) result in an RWInternalErr being thrown by RWTHROW. The asString() family of functions always return the string "#INVALID#" when called with an invalid RWDateTime.

The following examples show several ways to construct an RWDateTime with an invalid state:

Sometimes it is convenient to have an RWDateTime that is valid yet holds no specific value. The Essential Tools Module includes the “null” state sentinel for this purpose. You can construct a null RWDateTime or use the constant RWDateTime::nullSentinel in construction by passing the constant RWDateTime::nullSentinel to the RWDateTime(rwint64) constructor. You can also use the constant in direct comparisons with the millisecond count returned by RWDateTime::milliSeconds().

Comparison operations for equality and inequality do work, with an RWDateTime in a “null” state always being less than a valid RWDateTime. Arithmetic manipulation of a null RWDateTime results in an invalid RWDateTime. Attempts to use any part extraction functions (day(), month(), extract(), etc.) result in an RWInternalErr being thrown by RWTHROW. The asString() family of functions always return the string NULL when called for a null RWDateTime.

The following examples show how to construct an RWDateTime with a null state, and demonstrate what happens when it is used in an arithmetic operation:

When sorting and searching for RWDateTime objects it is useful to have sentinels that represent “smaller than the smallest” RWDateTime and “larger than the largest” RWDateTime. The “past” and “future” sentinels are special kinds of invalid sentinels.

RWDateTime includes two global static constants to determine the minimum and maximum valid RWDateTime objects: RWDateTime::minDateTime and RWDateTime::maxDateTime. You can pass these constants to the RWDateTime(rwint64) constructor to create instances of the minimum and maximum RWDateTime as needed, or you can use them to compare directly with the millisecond count returned by RWDateTime::milliSeconds().

The past and future sentinels can be used in any relational operation, and every valid RWDateTime falls strictly between the past and future sentinels. Arithmetic manipulation of past or future sentinels does not change their values, nor cause any error. Attempts to use any part extraction functions (day(), month(), extract(), etc.) result in an RWInternalErr being thrown by RWTHROW. The asString() family of functions always return the string "#INVALID#" for past and future sentinels.

Here are some examples of constructing and using past and future sentinels:

RWDateTime also provides for the use of 128 user-defined sentinels numbered 0 through 127. Each of these sentinels behaves like the null sentinel for part extraction functions, arithmetic manipulation, and relational operations. The asString() family of functions return "#>num<#" where num is the user sentinel number. The static method RWDateTime::userSentinel(int) is available for constructing user sentinels. These can be used to define different kind of dates, such as “refused”, for cases where a user has declined to enter data in a date field.

Here is an example of constructing and using user-defined sentinels: