In theory flights can be performed with zero visibility from start to landing. That of course sounds quite scary and certainly puts the flight crew under a lot of stress - which is why larger aircraft for commercial service are not flown by a single pilot. IFR is the way to go at night also when the country you want to fly in or through does not allow VFR at night.
IFR stands for “Instrument Flight Rules” and allows a pilot who is Instrument Rated (IR) to operate an aircraft by relying almost solely on instruments. Once a pilot holds a PPL, the next step is to be Instrument Rated (IR), allowing the pilot to fly IFR.
IFR permits an aircraft to operate in instrument meteorological conditions (IMC), which is essentially any weather condition less than VMC but in which aircraft can still operate safely. Use of instrument flight rules is also required when flying in "Class A" airspace regardless of weather conditions.
Here you can get training experience which is customized to each pilot and type-specific for the student's airplane. Multi-engine recurrent training involves a combination of simulator-based and airplane-based training per each pilot's preference. Multi-engine training programs are all type-specific and airplane-specific with the goal of reviewing both normal and emergency procedures appropriate to a particular airplane make and model and to the installed equipment.
The length of time it takes to earn your Instrument Rating depends upon how often you fly. You can receive your Instrument rating in as little as 30 days if you fly everyday. Most students fly on average 2-3 times per week.