How to apply time filter for today, last month, and last quarter in Splunk dashboard?

[Lavender]

Hi,

I have a requirement to show the data based on period . Period is a dropdown having Today,Last Month & Last Quarter. Based on this filter panel should refresh . 

My query is  

<input type="dropdown" token="period_tkn">
<label>Period</label>
<choice value="Today">Today</choice>
<choice value="Last Month">Last Month</choice>
<choice value="Last Quarter">Last Quarter</choice>
<change>
<condition value="Today">
<set token="er">"@d"</set>
<set token="lt">now()</set>
</condition>
<condition value="Last Month">
<set token="er">"-1mon@mon"</set>
<set token="lt">"@mon"</set>
</condition>
<condition value="Last Quarter">
<set token="er">"-3mon@mon"</set>
<set token="lt">"@mon"</set>
</condition>
</change>
<default>Today</default>
<initialValue>Today</initialValue>
</input>

<table>
<search>
<query>

index="index name" earliest=$er$ 
| where _time&lt;$lt$ AND _time&gt;relative_time(now(),$er$)
| table infra_on_prem app_name platform_name _time
| timechart limit=0 span=1h min(infra_on_prem) by platform_name
| eval hour=strftime(_time,"%H"),hour=_time."#".hour.":00"
| fields - _time
| transpose 0 header_field=hour column_name=Platform
| search Platform!="_span"
| addtotals
| eval Health=case(Total&gt;20,"100:::",Total&lt;1,"500:::",1=1,"300:::")
| fields Platform Health *
| `icon_indicator_stack`
| fields - Total
| transpose header_field=Platform
| rex field=column "#(?&lt;hour&gt;.*)"
| fields - column
| transpose 0 header_field=hour column_name=Platform
| rename "row "1 as Health

above query is for period="Today",  bolded query condition should change based on period filter . How can I do that . please help