Time-based planning and spreading enables setting a Metric, say Sales $ for a quarter, half-year or year and spreading the updated value to individual months and weeks proportionally.
Say you want to grow the total Sales $ for full year by 10%. You likely want to keep the contribution of each month consistent. Time-based planning and spreading allows you to set a value for Sales $ full year and spread the expected sales to each month and week proportionally.
See below for how it works in action: