Time axis from variables

[Tony Jolibois <tjolibois@xxxxxx>]

         Hi ferreters,

I'm trying to plot Argos buoy location with a time axis.
The data are in ascii file, so I read this page to create my time axis : 
http://ferret.pmel.noaa.gov/Ferret/FAQ/axes_and_data/time_axis_from_variables.html.
In the end of the page, you can find that :

Note that Ferret variables are represented as single precision real numbers.  
(Axes are represented in double precision, but we are using a variable to define
the axis and that variable is single precision.) If your timestep is small, such 
as minutes, and your times are a century or more after 1-jan-1900, you will need
to use a time origin later than 1-Jan-1900

The problem is that my timestep is so small that enven if I use a new 
time origin some step which was not equal are equal after the calculation.
Can someone know how can I define a variable with a better precision, or 
tell me what can I do to define a good time axis ?

Thanks in advance,
Tony