# Mechanics of futures contracts: with respect to which time reference is the variational margin calculated?

Consider the following situation. My futures exchange, Futures Inc., is open for business 9AM till 5PM EST. A few days ago I assumed a long position in a futures contract, $C$, on one unit of some underlying asset $A$, to be delivered at time $T$, two months from today. Futures Inc. releases price quotes on futures on $A$ every hour.

Now, suppose at 9AM the quote on futures on "$A$ with expiry date of $T$" is $1$ USD, and at 10AM the quote on the same kind of futures has risen to $3$ USD. At 10:05AM I decide to sell $C$ and promptly sell it for $3$ USD. At 11AM the quoted price is goes up to $4$ USD and at the end of the day, delivery price of futures on "$A$ with expiry date of $T$" is $5$ USD.

Now here are my questions, pertaining the changes in my margin account following this trade.

1. When do I see a change in my margin account? Just after the sale, at 10:05AM? Just after the next time tick, at 11AM, or just after the end of the day, at 5PM?

2. What will be the change in my margin account?

(a) $0$ USD - I have sold the contract, so I don't have a margin account any more,

(b) $1$ USD - the difference between the quoted price at the two time ticks between which the sale took place,

(c) $2$ USD - the difference between the last quoted price at the time the sale took place and the quoted price at the beginning of the trade day,

(d) $3$ USD - the difference between the quoted price at the next time tick following the sale and the beginning of the day,

(e) $4$ USD - the difference between the quoted price at the end of the day and the quoted price at the beginning of the day.

3. Am I eligible to withdraw the funds in my margin account? If so, when can I do it: just after the sale or after the end of the trade day?

4. What will be the change in the margin account of the person I sold $C$ to at the end of the day,

(a) assuming this person holds on to $C$?

(b) if they sold $C$ out prior to 4PM?