timestamp & graph time scale

Hi All,
This is my very basic question.
I have follwing table in database.
        result_time         | epoch | nodeid | light |
parent | voltage
----------------------------+-------+--------+-------+--------+---------
 2004-12-09 16:44:43.501375 |     1 |        |       |
       |
 2004-12-09 16:44:43.564375 |     2 |     10 |   362 |
     0 |     479
 2004-12-09 16:44:43.626375 |     3 |     10 |   408 |
     0 |     478
 2004-12-09 16:44:43.689375 |     4 |     10 |   429 |
     0 |     478
 2004-12-09 16:44:43.751375 |     5 |     10 |   438 |


I need to plot the light Vs Time.
 For plotiing the data I am using G2Dint java API. To
plot time on x axis I need to convert time to some
integer value (suppose I  choose  x-axis scale in
minute)
How can I convert Timestamp time to an integer minute.
As my database is having data over months of period,
actually I need to plot values Vs time. Is there any
Idea so that I can plot light Vs time ( and can show
date along with time). IFAIK G2Dint takes float or
integer values to plot them along x axis and y axis.
How can I show the time on X axis (with date).
Thanks for help.
Regards:
santosh dwivedi

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