Rule reminder
Register is determined by audience, medium, and purpose. A tweet can use any idiom; a legal contract cannot. A conversation with friends welcomes color and humor; an academic paper requires precision and neutrality. For each context, ask: who is reading/hearing this, and what level of formality do they expect?
A blogger is writing a personal piece about the Italian startup scene. She writes: 'Molti founder italiani rimandano le decisioni difficili alle calende greche.' Is this appropriate?