It sounds like you want to create a Date Range. Adobe Analytics defaults to hold 25 months worth of data, plus the current month. Your contract may differ.
While creating a date range with your start date fixed will certainly include all data, this will eventually include more months than you have data and any time-based visualization (like a line chart) using this date range will visually include dates that no longer have data.
Instead, I'd suggest creating a date range with the logic in my screenshot - start of current month minus 25 months, through the end of the current day (or hour or minute). This date range will dynamically remove old data as it becomes inaccessible after 25 months and not show any dates with expired data.