11th hour of the 11th day of the 11th month
Poppy Day is also referred to and known as Remembrance Day. For children, schools or anyone who may want to know how this day came about, there is useful reference material at Remembrance_Day. For other reference materials look here: d-day-6th-june.
Poppies and Heroes
You can help: http://www.poppy.org.uk/support-us/give-money