Yes, there is a way to overcome this issue. You can use a combination of custom number formatting and a helper column to create monthly separation tick marks on the x-axis.

Here are the steps:

1. Create a helper column next to your date column. In the first cell of the helper column, enter the formula "=TEXT(A2,"mmm yy")" (assuming your date column starts in cell A2). This will extract the month and year from the date and format it as "mmm yy" (e.g. "Aug 05").
2. Copy the formula down the helper column for all the dates in your data series.
3. Select your chart and go to the "Format Axis" pane.
4. Under "Axis Options", set the "Minimum" to the first day of the first month in your data series (e.g. "01 Aug 05").
5. Set the "Maximum" to the last day of the last month in your data series (e.g. "31 Jan 07").
6. Set the "Major unit" to "1". This will ensure that there is a tick mark for every day on the x-axis.
7. Under "Number", select "Custom" and enter the format code "mmm yy" (without the quotes). This will format the dates on the x-axis as "mmm yy".
8. Under "Axis Options", set the "Tick mark type" to "Outside". This will ensure that the tick marks are visible outside the chart area.
9. Under "Axis Options", set the "Tick mark spacing" to "1". This will ensure that there is a tick mark for every day on the x-axis.
10. Under "Axis Options", set the "Tick mark labels" to "Low". This will ensure that the tick mark labels are aligned with the axis.
11. Under "Axis Options", set the "Tick mark label position" to "Next to axis". This will ensure that the tick mark labels are visible next to the axis.
12. Finally, hide the helper column by selecting it and setting the font color to white.

Now your chart should have monthly separation tick marks on the x-axis that are aligned with the first day of each month.