Chart legend (X axis) to be in a direct timeline

[#1]

I want the chart legend (X axis) to be in a direct timeline 

I also want the blank months to appear.

Example:

Dimension

=IF(REGION_COST=REGIAO_REVENUE, IF(MONTH_COST=[Mês do calendário - Revenue, Date#((YEAR_COST & '/' & MONTH_COST),'yyyy/mmm' )))

Expression:

Revenue: Sum(revenue)

Cost: Sum(Cost)

In this case, 2012/APR has not been shown, because the value for the cost do not exist.

How do I unlink the expressions?