Functions with differences between engines
Calculation function  Difference 
ALL aggregation function  In Polaris, the default value for cells not mapped with the ALL aggregation function is FALSE. In the Classic Engine, the default value is TRUE. 
ADDMONTHS  In Polaris, if you use a value of NaN (Not a Number) for the Number argument, the ADDMONTHS function returns a blank value. In the Classic Engine, a value of NaN used with ADDMONTHS is equivalent to 0. 
ADDYEARS  In Polaris, if you use a value of NaN (Not a Number) for the Number argument, the ADDYEARS function returns a blank value. In the Classic Engine, a value of NaN used with ADDYEARS is equivalent to 0. 
CODE  In Polaris, if you use a time period value for the Item argument, the CODE function returns a blank text result. In the Classic Engine, if you use a time period value for the Item argument, the CODE function returns the time period value as text. 
FIND  In Polaris, the FIND function considers the length of all Unicode characters to be one. This means that the FIND function returns the correct starting character. In the Classic Engine, the FIND function considers the length of:

FINDITEM  You cannot use the FINDITEM function with Time in Polaris. In the Classic Engine, you can. 
HALFYEARTODATE  In Polaris, you can use the HALFYEARTODATE function with line items with a time scale of HalfYear. In the Classic Engine, you cannot. 
HALFYEARVALUE  In Polaris, you must enable Halfyear Totals in the Model Calendar to use the HALFYEARVALUE function. In the Classic engine, you can use the HALFYEARVALUE function regardless of if Halfyear Totals is enabled in the Model Calendar. In Polaris, you cannot use the HALFYEARVALUE function in a result line item with a time scale greater than the function. The Classic Engine returns a value of 0 in this case. 
ISBLANK  In Polaris, the ISBLANK function considers a text value that consists exclusively of carriage return characters to be a blank value. In the Classic Engine, the ISBLANK function considers a carriage return to be a nonblank value. 
ISFIRSTOCCURRENCE  In Polaris, you can use the ISFIRSTOCCURRENCE function with the Time list. In the Classic Engine, you cannot. Additionally, in Polaris, the ISFIRSTOCCURRENCE function does not have a 50 million cell limit as it does in the Classic Engine. 
ISNOTBLANK  In Polaris, the ISNOTBLANK function considers a text value that consists exclusively of carriage return characters to be a blank value. In the Classic Engine, the ISNOTBLANK function considers a carriage return to be a nonblank value. 
LAG  In Polaris, you can use numeric expressions for the Offset amount argument when you use a data type other than number for the Value to offset argument. Any number used for the Offset amount argument is rounded to the nearest integer. In the Classic Engine, if you use a data type other than number for the Value to offset argument, you can only use numbers for the Offset amount argument, not numeric expressions or the results of line items. Any number used for the Offset amount argument is rounded towards zero. 
LEAD  In Polaris, you can use numeric expressions for the Offset amount argument when you use a data type other than number for the Value to offset argument. Any number used for the Offset amount argument is rounded to the nearest integer. In the Classic Engine, if you use a data type other than number for the Value to offset argument, you can only use numbers for the Offset amount argument, not numeric expressions or the results of line items. Any number used for the Offset amount argument is rounded towards zero. 
LEFT  In Polaris, the LEFT function behaves as expected with all text values, including those that contain composite characters or characters from outside the Basic Multilingual Plane (BMP). In the Classic Engine, the LEFT function considers the length of:

LENGTH  In Polaris, the LENGTH function behaves as expected with all text values, including those that contain composite characters or characters from outside the Basic Multilingual Plane (BMP). In the Classic Engine, the LENGTH function considers the length of:

LOG  In Polaris, the LOG function returns a value of NaN (Not a Number) if you use positive infinity for the Base argument. In the Classic Engine, the LOG function returns 0 if you use positive infinity for the Base argument. 
LOOKUP  In Polaris, you cannot use the LOOKUP function in a result line item with a time scale greater than the values you look up. The Classic Engine returns a value of 0 in this case. 
LOWER  In Polaris, you cannot use the Locale argument with the LOWER function. In the Classic Engine, you can use the Locale argument. 
MID  In Polaris, the MID function behaves as expected with all text values, including those that contain composite characters or characters from outside the Basic Multilingual Plane (BMP). In the Classic Engine, the MID function considers the length of:

MIN  In Polaris, when comparing a blank date value to a nonblank date value, the MIN function returns the nonblank value. In the Classic Engine, when comparing a blank date value to a nonblank date value, the MIN function returns the blank value. 
MIN aggregation function  In Polaris, the default value for cells not mapped with the MIN function is blank. In the Classic Engine, the default value is 23991231. 
MONTHTODATE  In Polaris, you can use the MONTHTODATE function with line items with a time scale of Month. In the Classic Engine, you cannot. 
MONTHVALUE  In Polaris, you cannot use the MONTHVALUE function in a result line item with a time scale greater than the function. The Classic Engine returns a value of 0 in this case. 
OFFSET  In Polaris, a value of NaN (Not a Number) for the Offset amount argument returns the Substitute value argument. In the Classic Engine, a value of NaN is equivalent to 0. 
Operators and constants  In Polaris, operators such as >, <, and = return a value of FALSE when used with blank date or time period values. In the Classic Engine, operators such as >, <, and = sometimes return TRUE when used with date or time period values. For example, a nonblank date or time period value is considered greater than a blank date or time period value. 
PARENT  In Polaris, the parent of Years within the Time list is All Periods. In the Classic Engine, All Periods has a time scale of Years, which means Years is the parent of Years. In Polaris, the results of formulas are not coerced into different timescales. For example, if a formula returns a result with a Months timescale in a line item with the Years timescale, the formula is invalid. In the Classic Engine, the results of formulas are coerced into different timescales. For example, if a formula returns a result with a Months timescale in a line item with the Years timescale, the Months value automatically converts to display in the Years line item. 
POWER  In Polaris, In the Classic Engine, 
QUARTERTODATE  In Polaris, you can use the QUARTERTODATE function with line items with a time scale of Quarter. In the Classic Engine, you cannot. 
QUARTERVALUE  In Polaris, you must enable Quarter Totals in the Model Calendar to use the QUARTERVALUE function. In the Classic engine, you can use the QUARTERVALUE function regardless of if Quarter Totals is enabled in the Model Calendar. In Polaris, you cannot use the MONTHVALUE function in a result line item with a time scale greater than the function. The Classic Engine returns a value of 0 in this case. 
RANK  You cannot currently use the RANK function in Polaris. In the Classic Engine, you can. 
RANKCUMULATE  You cannot currently use the RANKCUMULATE function in Polaris. In the Classic Engine, you can. 
RIGHT  In Polaris, the RIGHT function behaves as expected with all text values, including those that contain composite characters or characters from outside the Basic Multilingual Plane (BMP). In the Classic Engine, the RIGHT function considers the length of:

ROUND  In Polaris, the ROUND function always uses the EXACT rounding method. In the Classic Engine, the ROUND function uses the NORMAL rounding method unless you provide EXACT for the Rounding method argument. 
SUBSTITUTE  In Polaris, the SUBSTITUTE function does not match the base characters of a composite characters. For example, the SUBSTITUTE function does not consider â to contain a or が to contain か. In the Classic Engine, the SUBTITUTE function matches the base characters of composite characters. For example, the SUBSTITUTE function considers â to contain a or が to contain か. 
TEXT  In Polaris, the TEXT function returns a text value of NaN when used with the numerical value NaN. In the Classic Engine, the TEXT function returns a blank value when you use it with the numerical value value NaN (Not a Number). 
TRIM  You cannot currently use the TRIM function in Polaris. In the Classic Engine, the TRIM function removes all leading and trailing spaces, and extra spaces between words in a text string. 
UPPER  In Polaris, you cannot use the Locale argument with the UPPER function. In the Classic Engine, you can use the Locale argument. 
VALUE  In Polaris, you cannot use the VALUE function with nondecimal representations of numbers (for example, In the Classic Engine, you can use nondecimal representations of numbers. 
WEEKDAY  In Polaris, you can use a decimal value for the Day offset argument and it is rounded to the nearest whole number. If you use a value outside of 1 to 7, the function returns a value of 0. In the Classic Engine, you must use a whole number for the Day offset argument. 
WEEKTODATE  In Polaris, you can use the WEEKTODATE function with line items with a time scale of Week. In the Classic Engine, you cannot. 
WEEKVALUE  In Polaris, you cannot use the WEEKVALUE function in a result line item with a time scale greater than the function. The Classic Engine returns a value of 0 in this case. 
YEARTODATE  In Polaris, you can use the YEARTODATE function with line items with a time scale of Year. In the Classic Engine, you cannot. 
YEARVALUE  In Polaris, you cannot use the YEARVALUE function in a result line item with a time scale greater than the function. The Classic Engine returns a value of 0 in this case. 
Functions not available in Polaris
Some functions, including most of the call center planning and financial functions are not available in Polaris. These include:
 AGENTS
 AGENTSB
 ANSWERTIME
 ARRIVALRATE
 AVGDURATION
 AVGWAIT
 COMPARE
 COUPDAYBS
 COUPDAYS
 COUPDAYSNC
 COUPNCD
 COUPNUM
 COUPPCD
 DURATION
 ERLANGB
 ERLANGC
 FIRSTNONBLANK aggregation function
 IRR
 LASTNONBLANK aggregation function
 MAILTO
 MAKELINK
 MDURATION
 NPV
 PRICE
 RANK
 RANKCUMULATE
 RATE
 SLA
 TEXTLIST aggregation function
 TEXTLIST calculation function
 TRIM
 YEARFRAC
 YIELD