How can I create a common dimension to show dates from more than one field

[fintan]

I have a table showing staff details

Column headings are

Staff No

StartDate

LeaveDate 

I want to create a chart that shows the count of starters & leavers each YearMonth

I can create a dimension StartDate.YearMonth or LeaveDate.YearMonth. How can I create a common dimension YearMonth? so I can show the count of starters & leavers each month? 

[vinieme12]

Main:
Load 
Staff,LeaveDate,StartDate
From Xyz;


DateBridge:
Load StartDate as Date
,'StartDate' as Datetype
Resident Main;
Concatenate(DateBridge)
Load LeaveDate as Date
,'LeaveDate' as Datetype
Resident Main;

//MasterCalendar:
//ADD Mastercalendar script here that links to Date field in DateBridge table

in Charts Use the Date field

example

Dimension :  Months(from master calendar)

Measure1:     # of Starters  = count({<DateType={'StartDate'}>}Staff)

Measure2:     #of leavers  = count({<DateType={'LeaveDate'}>}Staff)

read below

https://community.qlik.com/t5/Design/Canonical-Date/ba-p/1463578

https://qlikviewcookbook.com/2015/05/better-calendar-scripts/