Both statements are correct. A calendar spread can be created with call options as well as put options. In a put option, the investor must buy a long-maturity put option and sell a short-maturity put option. On the other hand, with call options, an investor must sell a European call option on the stock and simultaneously buy a European call option with a longer expiration date or maturity. A bullish calendar spread involves a strike price higher than the current stock price (where the options are out-of-the-money for calls but in-the-money for puts), while a bearish calendar spread involves a lower strike price.