Not only can you change the view option as described above, but you can also: 

• enter the duration or workload in hours  (by putting an "hr" bethind the number of hours).  To be noted:  you have to use a decimal notation, i.e 1,5hr for 1 hr and 30 minutes.
• change the Tool/Option/Schedule settings to say that you allways want to ender the durations in hours
• change the display of the gant chart by rigth-cliching on the header of the timescale, chose "timescale".  THere cou could set up to display the first tier as days, and the second tier as hours.  This is very usefull if you want to visualise tasks at the level of the hour (or even minutes)

Excel would not be the best solution to calculate peak resource consumptions and things like that.  Recalulation of start hours may be very usefull in case of dependencies.  However you prefer to stick to fixed dates, you can avoid the dependencies, or put a constraint "Has to start on". in the task details.