There are times you may be in a hurry to get a patent. In the US, you can avail the option of filing a Provisional Application for Patent (that resembles the format of a regular utility patent application), along with a Provisional Cover Sheet at the patent office for a fee. You will need to provide detailed information about the invention, but not to the depth required in the regular application.
This will ensure a registration date for your invention that is well ahead of the date of ultimate patent issue after filing the regular application, once you ensure that this regular application is filed within a year. But remember that this in no way resembles a regular utility patent, as it expires in a year's time, cannot be searched, and "it does not start a 20 year patent term running".
Provisional Applications are usually filed for reasons of non-availability of time, necessity of extra time to assess marketing strategies or insufficient finances to meet utility application needs. However, there is matching logic for not filing the Provisional -
US patent laws have been amended to allow upgrading of the Provisional Application into a Utility patent application. But be aware that this route to formally filing the utility application, though seemingly convenient, is fraught with complications and entails higher expenses that can be avoided by filing the utility patent application anew.