"six-month mark" is correct and usable in written English.
It is used to indicate a point in time six months after an event or occurrence. For example, "We will be evaluated for our success at the six-month mark since we started the project."
I remember worrying in the early months of pregnancy that, some time around the six-month mark, my mind would go to mush and all judgment desert me - because everyone said it would.
In the Chicago group, which has been meeting since April 2008, seven of nine members have been out of steady work for six months or longer; the other two are approaching the six-month mark.
He recently passed the six-month mark of his presidency.
The six-month mark, in February, coincides with the Chinese New Year, providing a chance for fresh marketing fireworks.
But by the six-month mark, subjects who relied on behavioral therapy alone made the most progress.
Sergeant Littlefield said he was struck by how quickly he reached the six-month mark in Iraq, compared to Kosovo.
With the first stroke of Big Ben, veterans and their families joined military chiefs at the Cenotaph in central London and observed a two-minute silence at the 11th hour of the 11th day of the 11th month, marking Armistice Day.
This Tuesday, the 15th May, marks the 70th anniversary of their existential loss and ongoing torment.
This past Wednesday – the 14th November – marked Europe's first coordinated anti-austerity strike action, drawing millions onto the streets across the continent.
The 10th of February marks the 68th anniversary of Mohandas Ghandi inventing The Master Cleanse Diet and I thought it only reich to revisit some WWII humor.
This Saturday, the 27th of January, marks the 73rd anniversary of the liberation of the Auschwitz-Birkenau concentration and extermination camps in the south of Poland, where approximately 1 million Jewish people were murdered by the Nazis between 1940 and 1945.
