How to Close existing financial year after 9 months

Our current financial year is April 1 2017-March 31 2018.we are planning to close this financial on December 31 2017 and start a new financial year from January 1 2018.
is it possible to create period voucher entry within this dates ?
if not possible can we do this from back end with the help of a developer ?

Check the following link

https://erpnext.org/docs/user/manual/en/accounts/tools/period-closing-voucher