There are two ways to filter for time on Dashboards. You can use the Time Filter at the top right of the workspace or you can use your Record Filters.
The Time Filter is only available if your data contains time stamps AND if the Primary Date was set on the Sources page during the upload.
At the top of the Dashboard you can select the specific time range you want to look at. The default setting is "all time", meaning you are text mining the entire time range, from the earliest date in the dataset to the most current.
If the Time Filter options are not available, you may need to re-upload the data. More on Uploading Data here.
Alternatively, you could use Record Filters to filter for time. Record filters are applied to a single dataset. The name is taken directly from the columns in the original dataset. Be sure to label your columns clearly. This filter can be applied to any date field, even if it was not originally set as primary date.
Record Filters for time ranges offer many options from “is” (a specific period) to choosing a date range after, before or between, etc.