Topic: Rollovers in Forex
Even though the mighty US dominates many markets, most of Spot Forex is still traded through London in Great Britain. So for our next description we shall use London time. Most deals in Forex are done as Spot deals. Spot deals are nearly always due for settlement two business days later. This is referred to as the value date or delivery date. On that date the counter parties theoretically take delivery of the currency they have sold or bought.
In Spot FX the majority of the time the end of the business day is 21:59 (London time). Any positions still open at this time are automatically rolled over to the next business day, which again finishes at 21:59.
This is necessary to avoid the actual delivery of the currency. As Spot FX is predominantly speculative most of the time the traders never wish to actually take delivery of the currency. They will instruct the brokerage to always rollover their position.
Many of the brokers nowadays do this automatically and it will be in their policies and procedures. The act of rolling the currency pair over is known as tom.next, which stands for tomorrow and the next day.
full article here