The DHS has created a system for generating events-based datasets from the calendar data,
where each change in the calendar becomes one observation, or ―row,‖ in a dataset. Each event
in the calendar--an episode of contraceptive use, a pregnancy, a birth, a termination, or an
episode of contraceptive non-use--is converted from the calendar string (the VCAL variables in
individual recode or woman-based datasets) into a separate observation for analysis. The start
and end date of each event is also recoded, allowing us to calculate directly the duration of the
event, women's age, women's parity, and children ever born (using the birth history) at the start
or end of each event.