Margin on futures for different months.

[markettiming]

Hello.
Could you tell me about margin. I attached printscreen below.
what do columns "start period" and "end period" mean?
i see different margin for each period.

 

[TWI]

The maintenance margin is the amount of money you need in your account per lot which will be held by the exchange. These are contracts for difference so your profit loss is just the difference in price of your entry and current price times the contract volume. The broker will also require a variation margin to give them security that you can cover daily price moves against you. your broker can provide a list of these amounts.
The maintenance margin is different for the different forward dates and that is what start time and end time refer to. These are futures contracts and there is a forward curve of contracts to trade. The further down the curve the less volatility in the price and so the less maintenance margin is demanded.

 

[trade2ysee]

This is simply futures expiration months ranges (because NG has expirations every month for next 12 years). More details are in specification