The time it takes to establish a cross connection in a data center can vary widely based on several factors. Cross connections involve the physical setup of cables, connections, and configurations to allow data to flow between different components or systems within the data center. Here are some factors that can influence the time it takes:

1. Complexity: The complexity of the cross connection plays a significant role. Connecting a few devices might be quicker than establishing connections between multiple racks or systems with different requirements.
2. Preparation: Proper planning and preparation can expedite the process. If all necessary components, cables, and configurations are ready in advance, the actual connection time can be reduced.
3. Cabling Distance: The physical distance between the components being connected matters. Longer cable runs might require more time for routing and securing cables.
4. Type of Connections: The type of connections being established matters. Simple Ethernet connections might be quicker to set up than intricate fiber optic connections.
5. Testing and Validation: Once the connections are physically established, thorough testing and validation are necessary to ensure that data flows correctly without disruptions. This testing phase can add to the overall time.
6. Existing Infrastructure: If the data center has existing infrastructure that needs to be worked around or integrated with, it can impact the time it takes for cross connections.
7. Workload and Resource Availability: The availability of skilled personnel, equipment, and tools can affect the time taken. If the data center team is busy with other tasks, it might take longer to allocate resources for cross connections.

Given these variables, the time to set up a cross connection can range from a few hours to a day or more. For straight forward connections, the process might be relatively quick, while more complex connections involving multiple systems, different types of connections, and extensive testing could take longer.

It's important for data center managers to balance the need for efficient setup with thorough testing to ensure the reliability and performance of the connections. Proper planning, experienced personnel, and streamlined processes can all contribute to minimizing the time required for cross connections.