Ms Preston with her camera shadowed Ms Clark through her campaign for the role of UN Secretary-General for most of 2016 while she was also carrying out her work as administrator of the United Nations Development Programme.
She went on the road with Ms Clark to Madrid, Botswana, Britain, Spain and Ukraine as well as the UN's New York headquarters.
"It was pretty demanding with all the camera gear as sometimes I would film it and other times I would have a film crew, but I am not as young as I used to be."
Ms Preston said Ms Clark's schedule was full on, as she would go between Beijing, Stockholm, Jakarta and Rio with a rest in New York, all in one week.
"She would treat planes like buses."
Despite the theme being about the need for women leaders to succeed and the film being set against the backdrop of Donald Trump versus Hillary Clinton, Ms Preston said the film was "quite funny".
"You see the press going around trying to find out things, then everybody else trying to keep everything away from them. It is quite a strange system but it was very funny."
Ms Preston said the documentary showed real resilience as they watched the selection of a Secretary-General from behind the shoulders of a leading candidate and they witnessed her "deal with and absorb major setbacks, get up and carry on".
Ms Whaitiri said to have someone capture Ms Clark's whole year and to see it through the lens of a local award winning filmmaker was "fantastic".
"I met Gaylene at a Maori film festival in Wairoa and she is such an amazing woman. It is so fortunate we can have Gaylene here after the screening to answer people's questions."
Ms Whaitiri encouraged people to attend tonight to witness a film that has received "great reviews" and "standing ovations".
Tickets can be purchased to the advanced screening at MTG Hawke's Bay in Napier online via premier.ticketek.co.nz/shows/show.aspx?sh=MYYEAR2017&v=NCT.
For more information about the film visit myyearwithhelen.com or www.facebook.com/MyYearWithHelenMovie.