Holyrood is a commemorative tartan, designed by Alistair Buchan of Lochcarron of Scotland to commemorate the Silver Jubilee of Queen Elizabeth II in 1977. Like a fashion/universal tartan it is to use by everyone.
Holyrood is also the name of the royal castle in Edinburgh, the Scottish equivalent of Buckingham Palace.
On the pictures below Holyrood kilts in two different lenghts, one of them a cheap 21" short light weight kilt which, depending on how I wear it, shall be either too short or just acceptable according to norms. The other one is 22.5" 5 yard 11 oz. wool kilt from Heritage of Scotland. Both are perfect in hot weather.