Unplanned absence
An unplanned absence is time away from work taken with little or no advance notice, whatever the reason behind it. It is defined by the notice, not the cause. Illness, a family emergency and a broken-down car all produce the same operational problem.
Planned and unplanned absence cost completely different amounts. The difference is not about legitimacy.
A day booked six weeks out gets covered during planning. The same day announced at 7am gets covered by somebody rearranging their morning, or not at all. Same absence, different disruption.
This is why notice is worth tracking separately from reason. The reason belongs in a leave record. The notice belongs in the cover conversation.
Making the notification path easy pays for itself immediately. Where telling somebody early means finding a manager who is not yet awake, people wait for the office to open. The team loses the two hours that would have let them rearrange.
Where this shows up in PeopleMuster
PeopleMuster stamps each leave request with its submission time, and shows a Today's Info panel of who is away now. Short-notice absence is visible the day it lands.
Questions people ask
Is short-notice leave the same as unplanned absence?
Close enough in practice. The distinction most teams draw is whether notice arrived in time to arrange cover, rather than any fixed number of days.
Should unplanned absence be approved retrospectively?
That is your policy's call. Most teams do, because the alternative is asking somebody to predict an emergency. The record still needs to exist either way.
How can unplanned absence be reduced?
Some of it cannot be, and pretending otherwise causes harm. What can improve is the notice path, so people can tell you early rather than at the last moment.