The confusion arises because the rules are somewhat different depending on whether the container is being used in a storage area or a satellite accumulation area to accumulate hazardous waste onsite without a permit.
Containers kept in a generator's hazardous waste storage area must be marked with the date that hazardous waste is first added to the empty container (the "accumulation start date"). That starts the accumulation period: 90 days for large quantity generators, 180 days for small quantity generators (or 270 days if the SQG has been granted an extension because of having to transport the waste 200 miles or more for off-site treatment, storage, or disposal). Failure to mark the accumulation start date on containers is one of the most frequent RCRA violations cited by EPA. When the applicable time period is met, the waste must be transported offsite for treatment, storage, or disposal, regardless of whether the container is full.
Generators that accumulate hazardous waste in satellite accumulation areas have different labeling requirements. In addition to ensuring that only one 55 gallon container for hazardous waste or 1 quart container for acute hazardous waste is being used "at or near any point of generation where wastes initially accumulate, which is under the control of the operator of the process generating the waste," the generator must mark the container with the date the container becomes full. The generator then has 72 hours (3 days) to remove the container from the satellite area to the hazardous waste storage area, ship it offsite, or manage it in an on-site permitted unit.
Of course, regardless of where the hazardous waste is being accumulated, each container must be labeled or marked clearly with the words "Hazardous Waste." Containers in satellite accumulation areas can alternatively be marked with other words that identify the content of the container.
Note that the requirements being described are the federal generator accumulation rules. Your state may have additional or somewhat different requirements.