Add and subtract operations
This table shows the valid combinations of types when the operator is + or . To understand the calculation of the expression A + B, find the intersection of the row for A's type and the column for B's type. Consult the numbered notes for the details of casting or conversion.
DateTime

Date

Time of Day

Integer

Decimal

Double

True or False

Other (text)  
DateTime

3  3  3  5  5  5  X  1 
Date

X  3  4  5  5  5  X  1 
Time of Day

X  4  3  X  5  5  X  1 
Integer

5  5  X  2  2  2  X  1 
Decimal

5  5  5  2  2  2  X  1 
Double

5  5  5  2  2  2  X  1 
True or False

X  X  X  X  X  X  X  1 
Other (text)  1  1  1  1  1  1  1  1 
X indicates that a casting, promotion or conversion is not supported. The Pega Platform reports an error.

For
+
, performs Java String concatenation (result is of modeSingle Value
). The minus operator (
) is not permitted. 
Converts
Integer
>Double
>Decimal
until both operands have same type, then perform operation. Result is of the promoted type. (Converts directly to the target type without performing intermediate conversions.) 
The
+
operator is not permitted. The
operator converts operands toDecimal
and performs the operation, yieldingDecimal
number of days and fraction of day. 
The
+
operator converts operands toDecimal
and performs the operation, yielding aDateTime
with GMT assumed. The  operator is not permitted. 
Converts operands to
Decimal
and performs the operation, yielding aDate
(rounded),Time of Day
orDateTime
(depending upon type of original nonnumeric operand)