We shall now adopt a new unit for time, the meter. One meter of time is the time it takes for light to travel one meter ... (page-4, Bernhard Schutz's A first course in relativity)
I am confused, how can one keep the unit of time and unit of length as same? It is later concluded that speed of light is unitless in this measuring system. Is this a valid unit change or is there some sort of abuse going on here?