I assume that this is P6 so go to edit users preference and turn the time on by going to the dates tab and at the bottom select Time 12 Hour.
Also click on the Time Units tab and change the decimals to 2 for unit of time and the Durations format.
Now go to the Projects Directory and select view show on bottom Project Details
make sure that you project is highlighted and go to the Date tab in the Planned Start box make sure that the TIME is 8:00 am or the earliest TIMES in all of the calendars that you are using.
IN the Data Date box make sure that the TIME is 8:00 am or the earliest TIME (or hour) in all of the calendars that you are using.
IN the Must Finish By Date box make sure that TIME is 5:00 pm or the LATEST TIME (or hour) in all of the calendars that you are using.
Go back to the activities directory filter for start milestones change and of the Primary Constrained Date TIME to 8:00 am or the earliest TIME (or hour) in all of the calendars that you are using.
filter for finish milestones change and of the Primary Constrained Date TIME to 5:00 PM or the latest TIME (or hour) in all of the calendars that you are using.
look at ALL of the original durations and remaining durations if any are in fractions of a day like 1.5 or 0.5 change these to whole numbers.
Look at your calendars and make sure that the TIMES are correct in all of the calendars that you are using for that project.
Press F9 and make sure that the TIME is 8:00 am or the earliest TIME (or hour) in all of the calendars that you are using.
That should correct it.