Yes, you can extend your goal end date. You can do so by clicking on "Edit Goal" in Goal Details section.
Related Question
How is the suggested amount to invest calculated?
Can I do mutliple investments against one goal?
Can I invest a lesser amount than the suggested amount?
Is there any penalty if I miss SIP payments towards my goal?
Is there any penalty if I miss RD payments towards my goal?
How is OnTrack or OffTrack status decided for my goal?
Can I stop SIPs midway before goal is completed?
I am unable to delete my goal.
Can I withdraw my savings before my goal is completed?
Can I extend my goal end date?
Yes, you can extend your goal end date. You can do so by clicking on "Edit Goal" in Goal Details section.