Sample Code:
<aura:component >
<aura:attribute name=”DayOfTheWeek” type=”String” default=”Monday” />
<aura:if isTrue=”{!v.DayOfTheWeek == ‘Monday’}”>
Today is {!v.DayOfTheWeek}
<aura:set attribute=”else”>
Today is not {!v.DayOfTheWeek}
</aura:set>
</aura:if>
</aura:component>
Cheers!!!