A very simple question, how do you judge how long somebody spends in the office? That question is not being asked in a negative sense, the professional working environment is typically one of salaried management who all work more than their contractual hours anyway, and there is no question of anyone getting a penalty. But purely for practical positive need, for example to objectively assess who most warrants limited office facilities, it might be useful to judge who spends most time using the base office versus time in other offices and other sites.
The obvious measure might be to record daily hours. But as stated above, salaried professional managers tend to work far more than official hours and they do not track their time on an hourly basis anyway. So we can look for other proxy measures of base office time.
The starting point could be a holiday and sickness report from the HR/Personnel department. That would have the basic number of days worked per year, though it would not say the working location.
One way to get that location might be to look at calendars. In a networked Office environment, it should be fairly clear who spends time in the home location, in meetings or in conference calls. But the calendar is only a plan of activity, it does not reflect the locations where working time is actually spent.
And if we simply ask people individually, apart from the subjective bias thus introduced, we should consider the responders' motivations and incentives. If there is a benefit to claiming more base office time, for example to justify better placed locations, then there will be a tendency for people to over-estimate that time. Most measures such as those I mentioned above are either incentive-neutral or equally prone to over-representation. Perhaps we need a measure that has the opposite intrinsic incentive.
Maybe look at travel expenses. Those who claim regular trips away from the base office probably have less need for base office facilities than those who do not.