There is no simple way to specify date and time formats for the minor tick labels. The most painless way to plot time and date along the X-axis is to double-click on the Tick Labels tab and select “Date” from the Type drop down list, then select a compound date and time format (e.g. 7/7/00 hh:mm:ss) from the Format drop down list. This will display date and time as major labels along the x-axis. If you wanted to do something like show date on the major labels and time on the minor labels, you could do something like this:
Create a data Double Y-axis graph (Plot: Special Line/Symbol, Double-Y).
Double-click on the Layer 2 icon and select Layer Properties.
Select the Link Axes Scales tab.
Set the Link X and Link Y axes as Straight 1 to 1.
Select the Display tab and check X-axes check box (under Show Elements).
Select the Size Speed tab and make sure that Units = % of Linked Layer.
You now have a double-Y axis graph with 2 x-axes displaying. Click on the Layer 1 icon and set X-axis Format to Date (e.g. 7/7/00) on the Tick Labels tab, set the scale range, increment, etc. on the Scale tab, and on Custom Tick Labels tab, offset the labels vertically (by, say, -150%) so that they don’t display over the top of Layer 2 labels. Now, select the Layer 2 icon and repeat these steps without offsetting the labels as you did for Layer 1.
This requires a bit of “messing around” but I think it will allow you to do what you want to do.
