Luke 3:23 says Jesus was "about [ὡσεί] 30 years of age" when He began His ministry. What does ὡσεί mean in this context? Does it allow for a few years or a few months plus/minus the given total of 30 years old? I have heard of people suggesting that it could allow for Jesus to be a few years older or younger than 30, yet it doesn't seem likely that Luke would be inaccurate in Jesus age while he was very accurate in other dates. I could really use some help in understanding this.
The English translations do not always carry the same connotations or flavor of the original Hebrew and Greek languages. The word is Strong's 5616 and is transliterated as "hosei". It means "as if, as it were, like; with numbers: about." In other verses - such as Matt. 3:16; 9:36; Luke 22:4; 24:11, Acts 2:3, etc - it is translated "as" or "like", the metaphor words which equate or compare one thing with another.
But, when using numbers or distances that involve measurements it is translated "about". In legalese, lawyers like to say "on or about May 22, 2015". They leave room for that small margin of error. Engineers / Technicians allow tolerances for a very small +/- mathematical variation.
The sense will not support the idea of a long period of years or months.
Num. 4:3, 23, 30 provide the ages of service in the tabernacle, or tent of meeting to be from 30 to 50 years of age. Jesus' service in the "temple" of His body would have conformed to the law and He would have been 30 years old, fit to be our High Priest after the order of Melchizedek (Psa. 110:4; Heb. 5:6, 10).
Note: Numb. 8:24 allows for apprenticeship for the younger Levites to begin at 25 years old, when they would have lighter tasks to perform in training for five years.
"and at twenty five years of age he entered into the service of the tent or tabernacle, where he was employed in lighter service, such as opening and shutting the doors of the sanctuary, keeping out strangers and unclean persons, and singing the songs of the sanctuary; but was not concerned till thirty years of age in carrying the vessels of the sanctuary on the shoulders, as the Kohathites; or in taking down and setting up the tabernacle, loading and unloading the wagons, as the Gershonites and Merarites; which is the business assigned unto them, and spoken of in Numbers 4:22, where the age of thirty years, and upward, is mentioned, as the time of their entrance on it, Numbers 4:23." See source: here