Well... I just downloaded Ext2.0.1 to verify this, and this is the code inside DatePicker:
Code:
var today = (new Date()).dateFormat(this.format);
this.todayBtn = new Ext.Button({
renderTo: this.el.child("td.x-date-bottom", true),
text: String.format(this.todayText, today),
tooltip: String.format(this.todayTip, today),
handler: this.selectToday,
scope: this
});
So... I think you are not using 2.0.1.
If the top line of your source says Ext 2.0, then you are using Ext 2.0 not 2.0.1, so this patch can't be work.
Try to go the the latest version 2.2 or 2.0.2 or override the full original onRender() method ...